Wells had the role of executive vice-president and chief operating officer with the squad, which he joined in 2007.
MWR, currently in its fifth season in the Sprint Cup Series, has had a lackluster season with Martin Truex Jr and David Reutimann, who currently rank outside the top-20 in the point standings, with no victories to their names and a second place for the latter at Kentucky as their only top-five finish of the season thus far.
The team also recently lost the services of Mike Coughlan as Director of Vehicle Design, after he left the outfit to join Williams as their chief engineer.
"We want to thank Cal for his strong contribution to getting Michael Waltrip Racing to where it is today. We wish him the very best in his future endeavors, " said team co-owner Rob Kauffman.
"We plan to go forward now with the solid management team that is in place, and bring MWR to the next level."
Wells, formerly an owner of PPI Motorsports, fielded cars in the Nationwide and Sprint Cup Series from 2000 and until joining MWR in their debut season, once his team was shut down.
He also enjoyed success in off-road racing and the now defunct CART series, winning once at Chicago with Cristiano da Matta.
