Brian Pattie, Juan Pablo Montoya's crew chief since May of 2008, has been replaced by Jim Pohlman, who takes over the role on an interim basis with immediate effect.
Following an inconsistent first half of the season for Montoya and his group, Pattie, who led the #42 team to a Chase berth in 2009, will be replaced from this month's Brickyard 400 onwards.
The Colombian and his team had enjoyed a solid start to their 2011 campaign but have steadily dropped in the point standings for a number of weeks, currently ranking 17th - their season lowest - and 59 points out the top 10 in the race for a place in the playoff.
After finishing a career-best eighth in the point standings in 2009, Montoya had a troubled 2010, when despite having a lot of speed he missed the Chase and finished 17th in the points with one win while his team-mate Jamie McMurray won three races although he too missed the playoff.
Last week Montoya ran out of fuel with more than a lap remaining at Loudon, despite making his final stop later than race-winner Ryan Newman.
Similar situations had hit Montoya and his team for the past year, which added to the inconsistent race showings that have taken a hit on the their hopes of making the Chase most likely triggered the team's decision.
Pohlman, 33, joined Ganassi in 2006 and has filled different roles within the organisation, more recently working with the engineering group in research and development.
Before that, he worked with Ray Evernham's outfit, having the car chief role for Bill Elliot when he claimed victory in the 2002 Brickyard 400, later serving in the same function within the organization but with Kasey Kahne as his driver.
"We are pleased to have someone of Jim's caliber to be able to place into this role on the #42 team. Jim has been with us a number of years and I have confidence in his abilities to move the team forward," said Chip Ganassi.
Despite Pattie being instrumental to Montoya making the Chase in 2009, the Colombian won only once during their 115-race tenure, out of a total 164 he has entered at NASCAR's top level. Pattie's sole Victory Lane appearance with Montoya came last year after a dominant showing at Watkins Glen.
A maiden win on an oval for Montoya was close with Pattie in a few occasions, most notably at Indianapolis last year when a four-tyre call on the final pitstop hampered them after dominating the race for the second year in a row.
Montoya's crew chief change is the third being announced over the last week by teams in the hunt for a place among the championship contenders in the 10-race playoff, which is only eight weeks from its start.