"We let him off the hook in the first couple of innings and he pitched pretty well after that," said Royals manager Buddy Bell. "It just wasn't a pretty sight tonight."
The Royals loaded the bases in the second on an infield single, a hit batter and a walk, but were turned away when Buck's sharp grounder was turned into a 3-6-3 double play.
"I squared up that pitch," said Buck. "If that's three feet to the right, the game's got a different feel to it."
Two walks and an infield single gave Kansas City another chance to score in the third, but that threat was snuffed out when Alex Gordon couldn't check his swing and was rung up to end the inning.
Buck said the early struggles left the Royals frustrated.
"That kind of flattened us, let the air out of our tires," he said.
Burnett kept Kansas City flat, retiring 10 of the next 11 batters before Buck's drive to left in the seventh, his second homer of the year.
Unlike the Royals, Toronto made the most of its chances against Odalis Perez. An RBI single by Reed Johnson and a three-run double by Lyle Overbay put Toronto ahead, 4-0, and chased Perez before the end of the second inning.
Bell was ejected when he argued that Johnson should not have been alowed to score from first on Overbay's hit because the ball was touched by a fan in the right-field corner, making it a ground-rule double. Plate umpire Paul Nauert called Johnson safe and Bell was ejected by crew chief Gerry Davis after coming out to argue.
"As far as Gerry's judgment, that's fine," said Bell. "That play, a lot of times, is not called the way it's supposed to be called and tonight, in his judgment, he thought the runner should be called safe. The thing I was upset about was Gerry said the runner was standing on third base when the fan touched the ball and I didn't see it that way. That was the disagreement.
Perez (0-2, 10.80) was charged with four runs on seven hits in 1 1/3 innings. He struck out one and walked one.
"Tonight he just couldn't find it at all," Bell said.
The Royals feared the worst when Mike Sweeney went down in a heap on a high-and-tight pitch from Burnett in the sixth. The ball grazed Sweeney's left hand but didn't do any damage, allowing him to stay in the game.
"It could have been a lot worse because it was up around my face," said Sweeney.
This is the fourth year in a row the Royals have lost their first road game of the season. It's also the fifth time Kansas City has kicked off its away schedule in Toronto. The Royals are 0-5 in those games.