Yankees manager Joe Girardi said that Eiland believes Rivera is throwing slightly off to the side of the ball, which has hurt his location and reduced the amount of cut on his pitches.
Catcher Jorge Posada said that some of Rivera's pitches in Sunday's appearance were up too much, like Ryan Kalish's one-out single to center field in the ninth inning. Kalish stole second and third base, scoring the tying run on a Bill Hall hit.
"It's frustrating," Posada said. "You want Mo to sail through -- you've got a 2-1 game, and they did a good job of really getting to some of his pitches and disrupting his tempo to the plate."
Girardi said that he believed the stolen bases -- two by Kalish, two by Hall -- were on Rivera, who has struggled some this year when forced to go to the slide step with runners on base.
"He was just slow, and I think his timing was predictable," Girardi said. "It did happen last night and I guess it shows that Mo is human. ... I think a lot of them were [off Rivera]. Actually, he's been really good about it. For whatever reason last night, he became a little predictable."
With many scouts in attendance at Yankee Stadium on Sunday, as well as an audience at home watching the nationally televised broadcast, Rivera said he couldn't be stunned if teams continued to try what worked so well for the Red Sox.
"Anybody can try whatever they want," Rivera said. "They have to make sure they get there. Those things don't bother me at all. As long as I execute my pitches and do what I have to do, I'm OK with that. It's not like I'm going to try something new -- been there, have done it. What am I going to see that's different, that I haven't seen?"
Rivera owned a 1.03 ERA after he was summoned to pitch two innings in a Sept. 10 extra-inning game against the Rangers in Texas. Girardi noted that Rivera has not had the same location and cut since then, as Rivera has blown three of six save opportunities -- after blowing just two in the previous 5 1/2 months.
"You want him to get his mechanical things worked out, and if he gets them worked out, you figure Mo is going to be Mo," Girardi said. "I don't see a big dropoff in velocity. The velocity has been the same all year, so physically I think he's OK. I just think he's a little out of whack. We've got to get him right."
Rivera bowed out of the All-Star Game in July, citing injuries to his right knee and left oblique muscle, and he said those ailments are still irritating him months later.
"I don't think when you play 162 games, you're not going to have problems," Rivera said. "I wish somebody would tell you that. Me, I won't tell you that. But you work with that. Everybody would love to be 100 percent and play, but I don't think there's one player that tells you that. Bumps and bruises, you have them, but you have to play with those things."