Former Detroit City FC coach Ben Pirmann on Thursday was named an assistant coach with expansion Memphis 901 FC of the second-tier USL Championship.

Detroit City announced his departure on Monday, terming it a mutual decision without providing any details.

Pirmann, 33, coached the semi-pro National Premier Soccer League club for the past six seasons, compiling a 49-17-17 league record and managing the team to three playoff seasons. He also was an assistant coach at his alma mater, Michigan State University, since 2011.

"I had been in talks with multiple clubs at the various professional levels in U.S. Soccer and had offers from a variety of teams as well as further college options," Pirmann said via email. "Memphis was the best fit with the most responsibilities and best for my personal development while getting out of my comfort zone for new challenges. Very tough to leave both families at MSU and DCFC."

In Memphis, he'll be an assistant coach under head coach Tim Mulqueen, a former MLS player.

"Ben is an exceptional coach who has a vast knowledge of the game," Mulqueen said in a statement. "He is a great teacher of the game who has developed many collegiate stars, as well as NPSL and USL players. Ben's work ethic will fit in perfectly with the Memphis 901 FC culture."

The Memphis 901 FC job is a step up for Pirmann in the soccer industry. USL Championship is second on the American soccer organizational pyramid, below only Major League Soccer. Detroit City FC and the NPSL are considered fourth-tier organizations, with mostly unpaid players who maintain their college eligibility.

The 36-team USL Championship was known until recently as the United Soccer League. Many of its teams have formal relationships with MLS clubs. Current USL Championship league winner FC Cincinnati became the most recent MLS expansion team.

One of Memphis 901 FC's co-owners is former U.S. Men's National team goalkeeper Tim Howard. The club is joining USL Championship in 2019 along with El Paso Locomotive FC, Hartford Athletic, Loudoun United FC, and New Mexico United. Memphis 901 FC will play at 10,000-seat AutoZone Park, a minor-league baseball stadium that is also home to Triple-A Memphis Redbirds.

Pirmann exits Detroit City as it prepares to become a professional club. It has grown its fan base to more 5,000 per game and garnered worldwide attention for functionally being a pro team with larger crowds than clubs in the second division. DCFC will play in the NPSL next year but then transition to the league's new fully professional league that's still being organized. It is conducting a search to replace Pirmann.

"A search for Pirmann's successor is currently underway and the club has convened an advisory group to assess a large portfolio of qualified candidates to manage its professional roster in 2019. There is no immediate timeline for naming a new head coach," DCFC said in a statement Monday.

Pirmann's DCFC resume includes a regular season title (2013), a Midwest Region championship (2017) and three NPSL playoff appearances (2013, 2015 and 2017). In 2017, he managed the team to a NPSL national semifinals penalty-kick loss to Midland-Odessa FC in front of a record home crowd of 7,533.

Pirmann in 2013 replaced Kylie Stannard, who coached DCFC to a 5-5-2 record in the inaugural 2012 season. Detroit City has subsequently grown a grassroots fan base to average 5,946 fans per match at Keyworth Stadium this past season, when the team finished 5-4-3. It had the NPSL's best attendance.

For his work with the MSU Spartans, who reached the NCAA Final Four this season, Pirmann was named the "National Top Assistant Coach" by College Soccer News in 2016 and 2017.