Since joining the program in 2012, he has been a part of all day-to-day lacrosse operations, with duties that include opponent scouting reports, recruiting, travel logistics, team meals, fundraising, social media, practice construction, and film exchange and breakdown. On the field, Kieffer primarily works with the offensive personnel players, goalies, and face-off players.

Most recently, the 2018 campaign saw Kieffer help lead the Dutchmen to the MAC Commonwealth Championship Tournament for the fourth consecutive season. Five players in Coleman Wagner (1T), Kevin Beaver (2T), Blake Weaver (2T), Cam Epple (2T), and Nick Mowry (2T) picked up all-conference recognition. Wagner and Beaver were recognized with Academic All-MAC accolades for their success in the classroom, while Wagner also became just the second player in program history to earn IMLCA All-Region honors (HM).

In the spring of 2017, LVC returned to the MAC Commonwealth Tournament after Austin Minnich (1T), Klayton Garman (2T), Wagner (2T), Epple (2T), and Barrett Campbell (HM) turned in all-conference seasons. Minnich was especially strong in earning IMLCA All-Region recognition for the second year in a row to go along with a spot in the USILA North/South All-Star Game. The senior also became LVC's first player to be named a USILA/Nike Scholar All-American. Garman was named the USILA National Player of the Week after setting a program record by scoring nine goals in a game and he joined Minnich as Academic All-MAC honorees.

In 2016, he helped the Dutchmen to another appearance in the MAC Commonwealth Championship Tournament before earning a berth in the ECAC Tourney. Five players in Koty Keefer (1T), Minnich (1T), Wagner (2T), Epple (2T), and Mowry (HM) picked up all-conference recognition, while Minnich was named IMLCA Second-Team All-Region for the first time in his career. Keefer and Minnich also excelled in the classroom and were pegged Academic All-MAC.

In 2015, he helped coach the MAC Commonwealth Rookie of the Year and second-team all-conference midfielder in Keefer, and MAC Commonwealth Honorable Mention attackman in Garman. He oversaw one MAC Commonwealth Player of the Week, two ECAC Players of the Week, and a pair of USILA Players of the Week. The Dutchmen reached the quarterfinals of the MAC Commonwealth and ECAC championship tournaments.

In 2014, Kieffer helped coach the program's first ever USILA All-American and ECAC All-Star in long pole midfielder Ryan Lanigan.