"A lot of people say that chemistry comes with winning," he said. "When you have a club that is winning, playing good baseball, then guys are having fun. Anytime things get testy in the clubhouse, it's when things are going in that direction."
That was the case in Boston, where the Red Sox underachieved as one of baseball's biggest disappointments this season after last year's September collapse.
As Mattingly has said throughout the non-waiver Trade Deadline when the team added major parts like Hanley Ramirez and Shane Victorino, the key is to just stick to the basics and get things done on the field. No matter how many All-Stars are on the team, the objective remains the same and chemistry will fall into place if the players perform.
In terms of any cracks in the clubhouse, he said it's up to him and the coaches to create a positive atmosphere and build a trust with the new players. That doesn't just happen overnight.
Mattingly said certain players, like Mark Ellis, are low maintenance. On the other end, there are guys who need more attention, and part of his job is to figure out how to manage them.
"The key is respecting what they do and what we do," Mattingly said. "We're dealing with men. It's not like we are dealing with kids that you can just tell what to do. There are relationships that are always being built and trust between coaches and the players."
Adrian Gonzalez clashed with manager Bobby Valentine while with the Red Sox and Josh Beckett was often under fire from the Boston media, which questioned his character and commitment on multiple occasions.
Both players said they are ready for the change of scenery and fresh start. Mattingly is confident the clubhouse will be just fine down the stretch.
"To me, I never expect problems," Mattingly said.
"I don't go into it thinking this is going to be bad. I'm not really worried about anything that could go wrong."