"We were kind of strapped in this moment, and we had to do something about it," manager Joe Maddon said.
A three-time All-Star, Bell was 1-1 with a 7.27 ERA in 13 appearances for the Rays after they acquired him from Arizona in December as part of a three-team trade that included Cincinnati. Tampa Bay still owes the right-hander $7,278,689 this season, though the Rays are receiving $3.5 million from the Diamondbacks as part of the deal to offset a portion of his $9 million salary.
That $3.5 million was money the Miami Marlins agreed to pay Arizona as part of a three-team trade that involved Bell in October 2012.
Karns was scheduled to start Sunday for Durham, so he provided insurance in case the Rays needed an extended outing from a reliever in the series finale against the Yankees. He caught a 9 a.m. flight for his first trip to New York City but did not get in the game.
"Here I am, ready to go," Karns said in the clubhouse about 2 hours before the first pitch.
Tampa Bay played a doubleheader Thursday in Boston and a 14-inning game Friday night at Yankee Stadium.
"We had to be protected here today," Maddon said. "We would have been totally naked had we not done something, so unfortunately it was Heath."
The 36-year-old Bell pitched 2 1/3 scoreless innings to earn the win Friday night, then was tagged for three runs and three hits while throwing 28 pitches in one inning Saturday.
"I wanted Heath to know, like, yesterday had nothing to do with it, because we knew that he was sucking it up for us yesterday," Maddon said. "I'm telling you, man, this guy's all about team."
Maddon acknowledged youth was a factor in the team's decision to keep 29-year-old righty Josh Lueke over Bell after "a lot of back and forth."
"We still see a pretty good upside with him," Maddon said. "We still think if he gets everything together that we're going to be rewarded by that patience."
Bell has 168 saves in 11 seasons with the New York Mets, San Diego, Miami, Arizona and Tampa Bay. He led the majors with 132 saves for the Padres from 2009-11.
Maddon said he had a "great conversation" with Bell on Saturday night.
"Total professional about this whole moment, explained the entire thing to him," Maddon said. "Hopefully we're going to get a chance to work together again soon."
Tampa Bay has 10 days to trade or release Bell, or to send him outright to the minors if he consents.