A 2007 Johns Hopkins graduate, this is Koesterer's second stint on the Blue Jay coaching staff as he had previously served at Homewood in 2011 and 2012.

Koesterer 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 7.77 goals allowed per game by the 2018 team is a UMBC single-season record. The Retrievers also finished eighth in the nation in man-down defense in 2018 and were ranked second in 2020.

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.

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 as faceoff specialists under Koesterer’s guidance.

In addition to his work with the Ohio State faceoff specialists, he 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).