2021: In 2021, Kempin played in a total of 10 matches, starting in nine of those for D.C. United. The 28-year-old goalkeeper recorded a total of 18 saves and kept a clean sheet in United's 1-0 victory over Chicago Fire FC in 1,817 minutes played.
Kempin joined Columbus Crew SC from the LA Galaxy on Dec. 17, 2017. In three seasons with the club, Kempin recorded 14 saves in eight appearances. The 27-year-old joined the San Diego Loyals in the United Soccer League (USL) Championship on loan on March 6, 2020. He made 10 appearances for the Loyals and recorded five clean sheets in 2020. He rejoined the Columbus Crew at the conclusion of his loan on Nov. 30, 2020.
The goalkeeper started his professional career on Aug. 30, 2010 when he signed with Sporting Kansas City (formerly the Kansas City Wizards) as their first Homegrown in club history. Kempin made his debut for Sporting KC in a 3-2 win against Orlando City SC (who were in the USL at the time) in the third round of the 2012 Lamar Hunt U.S. Open Cup on May 30, 2012. Kempin also made eight appearances for Sporting KC in the MLS Reserve League, recording two clean sheets.
The Leawood, Kansas native joined Orlando City SC in the USL on loan on March 14, 2013. In one season, Kempin recorded two clean sheets in nine appearances in league play. After rejoining Sporting KC at the conclusion of his loan, Kempin went back out on loan with another USL club, Oklahoma City Energy FC, on March 17, 2014. In one season, he recorded five clean sheets in 13 appearances. He was recalled to Sporting KC on June 30, 2014 and made four appearances (three starts) in MLS Regular Season Play, where he recorded five saves that season. Kempin also appeared in Sporting KC’s 1-1 draw with Real Esteli FC (Nicaragua) in the 2014 Concacaf Champions League on Aug. 20, 2014.
The six-foot-one-inch goalkeeper joined San Antonio Scorpions FC in the North American Soccer League (NASL) on loan on March 20, 2015 and made two appearances before rejoining Sporting KC. In 2015, he made four appearances for Kansas City including a substitute appearance in the 2015 MLS Cup Playoffs against the Portland Timbers. Kempin then joined Swope Park Rangers in the USL Championship on March 25, 2016. He recorded three shutouts in 12 appearances in the USL that season. At the conclusion of his loan, Kempin was released by Sporting KC at the end of the 2016 season. He signed with the LA Galaxy on March 3, 2017 and had stints with the first team and LA Galaxy II in the USL Championship. Kempin recorded 27 saves in seven appearances with the LA Galaxy in MLS play and also recorded two clean sheets in six appearances for LA Galaxy II in 2017 before being traded to Columbus Crew SC.