"I still have to be more consistent. I let fastballs get up. When the weather started getting out of control, you have to slow the game down and not get ahead of yourself," Chamberlain said. "The bullpen has done a good job so far. There's no second-guessing the bullpen."
Alberto Callaspo added an RBI single. Buck, who had three hits, doubled home Callaspo with the final run.
"I blew the game," Coke said. "I didn't give myself a chance by getting ahead of the hitters. When you don't do that, you give them a chance. I don't have any excuses. I stunk it up pretty bad and ended up costing Joba a win."
"We came back and got it done," Royals starter Gil Meche said.
Chamberlain, who made 12 starts last season before going on the disabled list with rotator cuff tendinitis and then going back to the bullpen, held the Royals to three runs -- one earned -- and four hits in six innings. He struck out five, walked one and hit two batters with pitches.
The right-hander came out after throwing 88 pitches, 56 for strikes.
The Yankees took a 4-3 lead with a three-run seventh. Nick Swisher and Hideki Matsui opened the inning with singles, followed by Xavier Nady's RBI double. Royals first baseman Mike Jacobs committed an error on Robinson Cano's bouncer, allowing another run to score. Nady came around with the go-ahead run when Melky Cabrera grounded into a double play.
Meche held New York to three hits through six innings before giving up three runs in the seventh.
"For me, a 3-1 lead going into the seventh inning, it's a situation we should have the game under control, especially the way I was rolling for a while," he said. "They just started hacking first pitch, got some balls in play. Swisher didn't hit the ball too hard, broke his bat, base hit. Then Matsui rolls over in the hole. Nady just hooked it down the line. I just tried to keep it under control as much as I could. I knew they were going to get some runs."
The Royals took a 3-1 lead with two unearned runs in the fourth thanks to Swisher's two-out error at first base. Callaspo's grounder went between Swisher's legs, scoring David DeJesus, who led off the inning with a walk. Buck singled home Mark Teahen, who was hit by Chamberlain's pitch, for the other run.
Buck had a solo homer in the third.
"Me and Brayan have an advantage already because we are catchers, so we're cool already," Buck said, laughing.
Brett Gardner, who led off the game with a single and stole second, scored the first Yankees run on Meche's wild pitch.
Meche went seven innings, allowing four runs and six hits with six strikeouts and two walks.
"It was a great feeling just to help my team win. I'm very happy," Brayan Pena said.
Yankees 1B Mark Teixeira was held out of the lineup for the second consecutive day with tendinitis in his left wrist. ... Royals 3B Alex Gordon did not play because of a sore right hip. ... The Royals are hitting a big league-low .201 with 14 runs in six games.