But it doesn't seem to be that way for Green Bay Packers running back Ryan Grant as he prepares to face the New York Giants in Sunday's NFC Championship game.
A week before the start of this season, New York dealt Grant to Green Bay for a sixth-round draft pick.
And what a steal he has been.
While Grant admits he might be "a little bit" more fired up to play his former team, how could he hold a brudge after the trade worked out so well for him?
"There were no hard feelings toward the organization in New York," Grant said. "I take the positive out of every situation, and there were a lot of things that I learned from there. And I feel like if I didn't learn that, I probably wouldn't be in the situation I am today."
Still, Packers coach Mike McCarthy plans to pull Grant aside this week just to make sure he isn't getting too wound up.
"I think he'll be fine," McCarthy said. "I don't think he'll be one of those guys that will be so revved up that he'll go the other way. I know this is a big opportunity for him. But he's a focused young man."
Grant took over as the Packers' featured back in Week 8.
His emergence since has given the Packers a two-dimensional attack. He was the leading man last week, rebounding from two early fumbles to finish with 201 yards rushing and three scores in Green Bay's win over Seattle.
But even if Grant isn't using revenge as motivation, Giants defensive end Michael Strahan wonders whether the move will come back to haunt them.
Especially after New York struggled to stop the run in its playoff victory at Dallas on Sunday.
"I am upset Ryan Grant is not with us," Strahan said. "He runs like a bull. ... That's one of those guys you look at and you think, 'We let him go and we let one get away.' "
Grant said he was "shocked" when the Giants traded him, soon after telling him he had made the team.
But New York's backfield was crowded with good players going into the season. Grant hadn't played a regular-season snap in his first two years in the NFL. So when the Packers called, the Giants listened.
Grant said his former teammates were stunned.
"I know that when they found out I had been traded, a few guys kind of said, 'What?' -- kind of a reaction of 'Why would you do that?' " Grant said.
Giants running back Brandon Jacobs said Grant is a "tremendous guy" with talent.
"He's done well for Green Bay," Jacobs said. "I think that was a great move for him. I think that served him very well, and he's done well for them."
But Grant knows that support only goes so far.
"I'm pretty sure that will stop come Sunday," Grant said. "I know it's nothing personal and we're competitors and I expect that."