With one out in the sixth, Andrew Benintendi advanced to second on a balk by Cobb. The right-hander clearly was not happy with the call.
Rays manager Kevin Cash explained what the umpires told him.
"No step with his lead leg, just a spin [to first base on the pickoff attempt]," Cash said.
Cobb told reporters he used the same move he's been using all season.
"If there is something illegal about it, I have not heard anything about it before," Cobb said. "Nothing happened, so to make something out of a nothing play is a little ridiculous to me. I understand if he sees something, he's naturally going to call it. But a lot of times, umpires will come to you between innings, or tell the catcher, 'OK, make sure he does whatever it is that's in question so I don't have to call him.'
"I don't know how many pickoff attempts I had before that, but it's the same one. So, just for that moment in the ballgame to make that call, it was confusing to me."
After advancing to second, Benintendi stole third base.
"Came to a set position and heard some screaming late and I don't know how he got down the line that quick," Cobb said. "I took my eye off him for a second; he must have timed me up some way."
The Rays pulled in their infield with Mookie Betts up. Cobb threw a 2-2 fastball that looked like a strike, which further displeased Cobb. Betts followed with an RBI single to left on the next pitch to put the Red Sox up, 2-0.
"I get these guys miss calls," Cobb said. "It's tough to do what they do. Just in that moment, one of the best hitters in the game is up and there's not too many ways you can get him out. But I thought I executed the pitch really well there. To change from really a strikeout to an RBI and a run scored later in the game. You can't predict what's going to happen in baseball. But the fact is it was a missed call and it turned into two runs after that."
After Benintendi scored on Betts' hit, Cobb chirped at home-plate umpire Jeff Nelson, and, apparently Logan Morrison did more than chirp as Nelson ejected the Rays' first baseman, who was not in the lineup.
"I think Lo-Mo was voicing his displeasure and backing his teammate a little bit," Cash said. "Was just frustrated."
Dan Jennings took over for Cobb and the Red Sox added another run, which was charged to Cobb.
"I haven't gone back and looked at [the pitch to Betts], but I could tell from the reaction of the guys coming up that it was a big pitch," Cash said. "We needed the pitch, it's unfortunate. It's tough to say one pitch decides outcomes of games, but it can really swing the momentum one way or the other. And ultimately that one did."
Bill Chastain has covered the Rays for MLB.com since 2005. This story was not subject to the approval of Major League Baseball or its clubs.