Mike was a star outfielder for John Bush from 1990 to 94 and lettered all four years at Washington Township High School, graduating in 1994.

Koerner was named All Group, All State and All South Jersey in 1993 and 1994. In 1993, Mike had a batting average of .500 with 44 RBI's and had 18 extra base hits. Mike helped Washington Township, in 1993 to capture the "Joe Hartmann Diamond Classic" Championship.

In 1994 he had a batting average of .418 with 32 RBI's and had 15 extra base hits. He was named the Gatorade High School Player of the Year. Also in 1994, went all the way to win the State Group IV Championship. He also took All Conference honors, in winning the Olympic Conference Championships in 1993 and 1994. After High School, Mike headed to Louisiana State University (LSU). At LSU, he was a member of the 1996 and 1997 National Championship teams and a member of the All College World Series Team in 1997. Mike was drafted in the 11th round by Oakland. He closed out his professional career in Single A' Dodgers' organization in 2000. Mike lives in Sewel, NJ