Coaches

Updated:  January 8, 2026
First Day at Johns Hopkins:  May 11, 2020

Jamison Koesterer, a 2007 Johns Hopkins graduate, was appointed the Blue Jay defensive coordinator on May 8, 2020 and was promoted to associate head coach on October 7, 2024.

Koesterer returned to Homewood in 2020 after serving four years in the same role at UMBC.

In addition to running the Blue Jay defense, Koesterer also provides assistance with the Blue Jay faceoff specialists.  His defensive units have been at the heart of the success the Blue Jays have enjoyed since his return, specifically during the 2023 and 2024 seasons.

Johns Hopkins posted a combined record of 23-11 in 2023 and 2024, including a 9-1 mark in Big Ten regular season play, advanced to the NCAA Quarterfinals twice, claimed a share of the 2023 Big Ten regular season title and won the 2024 Big Ten regular season title outright. 

Johns Hopkins finished seventh in the nation – and first in the Big Ten - in scoring defense in 2024 (9.63) and a set a program record for caused turnovers per game (8.25).  Two Johns Hopkins defensemen and one short stick defensive midfielder earned All-America honors in 2024, when the Blue Jays held 11 of 16 opponents to 10 goals or less and 15 of 16 were held under their season scoring average.  The 9.63 goals allowed per game in 2024 were the fewest by Johns Hopkins since 2014.

Koesterer’s defense sparked the team’s run to a share of the Big Ten regular season title and the NCAA Quarterfinals in 2023 as JHU allowed just 11.06 goals per game.  Three All-Americans - Alex Mazzone, Scott Smith & Brett Martin - anchored the unit and JHU set a school record with 135 caused turnovers.

The top four single-season averages for caused turnovers per game and the top three single-season caused turnover totals have come under Koesterer’s direction.

In his first season as the defensive coordinator in 2021, Koesterer helped guide the Blue Jays to their third consecutive appearance in the Big Ten Championship game, where they narrowly fell, 12-10, to top-ranked and eventual national runner-up Maryland.

Koesterer’s group was at its best during the team’s three games against third-seeded Penn State, second-seeded Rutgers and top-seeded Maryland in the Big Ten Tournament.  In six games against those teams during the regular season, the Blue Jays allowed an average of 13.5 goals per game; during the three-game run in the tournament, Hopkins cut that number down to 9.7 (29 goals in three games).

Prior to returning to Homewood, Koesterer had joined the UMBC coaching staff in July 2016 and quickly made an impact on the Retriever defense. His unit finished in the top 20 in scoring defense in 2017 (19th/9.14), 2018 (1st/7.77) and 2020 (6th/8.40).

The Retrievers also finished eighth in the nation in man-down defense in 2018 and second in 2020.

Koesterer helped guide the Retrievers to the 2019 America East title and a first-round victory in the NCAA Tournament.

Prior to his time at UMBC, Koesterer spent four seasons at Ohio State and helped the Buckeyes to a pair of trips to the NCAA Quarterfinals (2013, 2015) while working with the defense and faceoff specialists. In 2013, his first season at Ohio State, the Buckeyes knocked off defending national champion Loyola in the ECAC title game to earn a berth in the NCAA Tournament for the first time since 2008.

While in Columbus, he coached the 2016 Big Ten Specialist of the Year in Jake Withers, while Withers (2014 – ECAC, 2016 Big Ten), Chris May (2015- Big Ten) and Trey Wilkes (2013 – ECAC) each earned all-league honors under Koesterer’s guidance.

Koesterer also assisted with Buckeye defenses that ranked among the nation’s best in 2013 (13th/8.83), 2015 (17th/9.16) and 2016 (19th/9.07).

Koesterer served as the volunteer assistant coach at Johns Hopkins in 2011 and 2012 and helped the Blue Jays to a two-year record of 25-7 with two trips to the NCAA Quarterfinals.  He mentored senior Matt Dolente to First Team USILA All-America honors in 2011, when he finished second in the nation in faceoff winning percentage (.667).

A year later, Koesterer’s faceoff unit finished seventh in the nation (.578) with junior Mike Poppleton leading the way by winning 167-of-271 (.616).

Koesterer played at Johns Hopkins from 2004-07 and was a member of Blue Jay national championship teams in 2005 and 2007.  He scored seven goals and added 12 assists and 101 ground balls during his career.  He also won 176-of-318 (.553) career faceoffs and helped guide the Blue Jays to a 51-11 record.

After graduating, Koesterer continued his playing career in the National Lacrosse League as a member of the Portland Lumberjax (2009) and the Washington Stealth (2010).  He helped the Stealth to the 2010 NLL Championship – the first title in franchise history – by winning 265-of-446 (.594) faceoffs while collecting 101 loose balls (the equivalent of a ground ball in indoor lacrosse).

Updated:  January 8, 2026
First Day at Johns Hopkins: August 3, 2020

Jon Cohen was named an assistant coach at Johns Hopkins on June 28, 2024 after spending four years as the Blue Jays’ Director of Operations. Cohen joined Peter Milliman’s staff in June 2020 and managed the day-to-day logistical operation of the program as the Director of Operations.

In his role as an assistant coach, Cohen works closely with the Blue Jay faceoff specialists, serves as the assistant defensive coordinator under the direction of defensive coordinator Jamison Koesterer and also serves as the program’s recruiting coordinator.

In his first season as an assistant coach in 2025, Cohen helped then senior Logan Callahan to one of the best seasons in program history by a faceoff specialist.  Callahan won 189-of-311 (.608) faceoffs and grabbed 106 ground balls.  He earned Honorable Mention All-America honors from Inside Lacrosse and Lacrosse Magazine and was a Second Team All-Big Ten selection.

Cohen came to Homewood after serving as the General Manager of Major League Lacrosse’s Denver Outlaws.  The GM post was the latest in a long line of positions Cohen held with Outlaws during a 14-year run with the team.

Starting as a visiting team liaison in 2007, he later served as the head equipment manager (2008-10), assistant general manager/assistant coach (2011-18) and director of player personnel (2018) before making the move to general manager prior to the 2019 season.

Cohen helped Denver to a 118-62 (.656) regular season record from 2007-20 with MLL Championships in 2014, 2016 and 2018.  The Outlaws also advanced to the MLL title game six other times and played in the title game every year from 2016-2020.  Denver’s 14-0 record during the 2013 regular season marked the first time in MLL history a team had gone through the regular season unbeaten.

Cohen graduated from UNLV in 2009 with a degree in hospitality management.  As a defender, he was a three-year member of the Runnin’ Rebels’ club lacrosse team.  He got his start in coaching as an assistant boy’s lacrosse coach at Bishop Gorman High School in Las Vegas and helped the team to the 2009 Nevada State Championship and also served as the head coach at Heritage High School in Colorado after graduating from UNLV.

Updated:  January 8, 2026
First Day at Johns Hopkins:  June 28, 2024

In his second season as a member of head coach Peter Milliman’s staff - and first as an assistant coach - is Chayse Ierlan, who was named the program’s Director of Operations on June 28, 2024 before being promoted to assistant coach on August 11, 2025.

In his new role, Ierlan works closely with Milliman directing the Blue Jay offense while also lending his expertise to the Blue Jay goalies.

In 2026, Ierlan will have the opportunity to guide an experienced, yet still young, group of offensive players while helping guide a deep and talented group of Blue Jay goalies.

As the Director of Operations, Ierlan coordinated all team travel, managed the team’s extensive video operation, arranged all recruiting visits and served as a liaison between the program and all internal and external constituents.  He also worked closely with the Department of Athletics administration on budget operations and other day-to-day activities associated with the program.

In 2024, Ierlan capped a standout college career that included one season at Johns Hopkins (2024) and four years at Cornell (2020-23).  He posted a 9.53 goals against average and .564 save percentage while helping lead the Blue Jays to the NCAA Quarterfinals in 2024.  

Ierlan ranked seventh in the nation in goals against average and eighth in save percentage; his 199 saves were the most by a Blue Jay goalie since 2008 and the second-most by a Johns Hopkins goalie this century.

Ierlan was a four-year starter in goal at Cornell and appeared in 52 games with 50 starts.  He was an Honorable Mention USILA All-American, USILA Scholar All-American and First Team All-Ivy League selection in 2023, when he posted an 11.13 goals against average and a .522 save percentage.

He helped the Big Red to an appearance in the 2022 NCAA Championship game and finished his Cornell career with an 11.40 goals against average and a .517 save percentage.

Updated:  January 8, 2026
First Day at Johns Hopkins: October 4, 2025

Braden Wallace is in his first year as the program’s Director of Operations after being appointed on October 4, 2025.  

As the Director of Operations, Wallace will coordinate all team travel, manage the team’s video operations, arrange all recruiting visits and serve as a liaison between the program and all internal and external constituents.  He will also work closely with the Department of Athletics administration on budget operations and other day-to-day activities associated with the program. 

Wallace brings an extensive lacrosse background to Homewood and most recently served as the Club Director for Klutch Lacrosse since 2024 while also serving as the offensive coordinator at the John Carroll School, which competes in the prestigious MIAA.  Arriving at John Carroll in the fall of 2022, he had an immediate impact on the Patriot offense as the team saw a nearly 100 percent increase in offensive production from his first season in 2023 to his second in 2024.

Prior to his time at John Carroll and with Klutch, he spent four years at the Director of Boy’s Lacrosse with the Edge Lacrosse Club (2018-2022) and was later the head coach of the 2023s and 2024s.  From his 2023-24 roster with Edge, more than 30 players went on to play college lacrosse, including 15 at the Division I level, including two current Blue Jays (Matt Collison, Chuck Rawson).  Wallace got his start in lacrosse at Webster Thomas High School, where he spent the 2018 season as the offensive coordinator.

Wallace graduated from RIT with a degree in marketing and was a four-year standout on the men’s lacrosse team.  He was a First Team USILA All-American as a senior and a third team selection as a junior.  A two-time First Team All-Liberty League selection and a two-time team captain, he played in 91 career games and rang up 94 goals and 47 assists for 141 points while helping the Tigers to four consecutive trips to the NCAA Tournament and a run to the national championship game as a senior.

The Buffalo Bandits selected Wallace in the 2017 National Lacrosse League Draft and he enjoyed a standout career with Burlington in the Ontario Junior A League as he played in 68 games and totaled 70 points with the Chiefs.