Yet through five starts, the Yankees still want to be convinced. The right-hander took a thumping in front of a national television audience on Sunday, serving up eight earned runs and exiting in the fifth inning as the Red Sox posted a 9-3 victory.
"I don't want to take anything away from these guys, but I think I would have gotten pounded by whoever I faced tonight," Burnett said. "I threw some balls in some good spots in hitters' counts. Especially against this team, you can't do it.
"You can get away with it some days, but they're just as geared up to face us as we are to face them. You've got to pounce when you get the opportunity, and I left them some opportunities."
Burnett admitted this spring that he might have been too emotionally caught up in what the rivalry entails, having come over and performed much differently than he did when he was wearing the colors of the Blue Jays.
It would seem Burnett is still searching to correct that. He has now allowed 31 earned runs in 22 innings pitched in Boston as a Yankee -- a 12.68 ERA -- after winning all three of his previous starts on Yawkey Way with Toronto.
"He's not making his pitches," said Yankees manager Joe Girardi, who was ejected in the fourth inning by home-plate umpire Tim McClelland. "His first start here wasn't too bad this year. Today he just struggled with his command. ... I'm sure he's frustrated by tonight."
Jeremy Hermida hit a two-run homer and had three RBIs, while Adrian Beltre cracked a two-run double to lead the Boston charge against Burnett, who also served up run-scoring hits to David Ortiz and Kevin Youkilis.
"I just threw balls over the plate," Burnett said. "That's kind of the bottom line. I felt I had a good hook tonight, but I didn't have a good heater. I had a good fastball early, but after that, everything was up. The ball to Ortiz leaked over; the one to Beltre was up. They all didn't go where they were supposed to go."
Burnett tied a career high by allowing nine runs -- one of which was unearned due to a Marcus Thames error -- while walking three and striking out four. Four of the five runs that crossed the plate in Boston's third inning came with two outs.
"I've still got to find a way to stop the bleeding," Burnett said. "They're an aggressive team, and if you leave balls up, they take advantage of you. That's what happened. Go figure."
Though Romulo Sanchez hurled 3 2/3 innings of scoreless, one-hit relief in his Yankees debut, it wasn't enough to keep Burnett from suffering his first loss in seven starts this year. Burnett is 0-2 with an 8.35 ERA in his past seven starts against the Red Sox.
Nick Swisher and Alex Rodriguez homered in the third inning to account for the only scoring against Red Sox starter Jon Lester, who limited New York to four hits in seven innings, walking two and striking out seven to win his third consecutive start.
"[Lester had] good command," Swisher said. "We had him on the ropes there for a little bit, but he got out of it. You know every time you face these guys, you're going to get their 'A' stuff. He had his game tonight, and they had their bats working as well."
A-Rod's homer was the 586th of his career, pulling him even with Frank Robinson for seventh place on baseball's all-time list. For Rodriguez, the shot over the Green Monster also snapped a personal homerless streak spanning 61 at-bats.
Robinson Cano chipped away at the deficit with a run-scoring single in the eighth inning off reliever Manny Delcarmen, but that would be the last surge, as New York's six-game winning streak came to an end.
Still, the Yankees have won nine of 10 series this year and have posted victories in 16 of their past 22 games, leaving them behind the Rays -- who fell victim to Dallas Braden's perfect game on Sunday in Oakland -- by just a half-game for first place in the American League East.
"We just have to continue to build on some of the things that we're doing well," Rodriguez said. "I think though we've played well, there's a lot of room for improvement. We know that. We need to continue to take series and do our jobs."
Burnett had commented after beating the Orioles in each of his two previous starts that he was beginning to feel more like himself than he had in a while, which is why it was disappointing for him not to be able to keep the Yankees in Sunday's game longer than he did.
While Girardi suggested that Burnett "knows he needs to" move on quickly from this outing, the right-hander suggested that he'd let it linger just a little bit longer than some others might.
"I'm not going to turn the page by the time I wake up tomorrow," Burnett said. "I'm going to think about it and go over what happened and why the balls cut, and this and that.
"It's not going to stop me. I'm feeling good where I am right now. It's a bump in the road. The good ones overcome that."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.