Kansas City, Mo. ? The Kansas City Royals finally got their first homer of the season out of the cleanup spot.

It was just about the only highlight on the night.

Tigers starter Rick Porcello cruised through seven sharp innings, and Detroit battered James Shields once again in an 8-2 victory Friday that opened their three-game series.

The home run came courtesy of Billy Butler, his first of the season. But it also came with the Royals already trailing 5-1 in the fourth inning, and the Tigers proceeded to tack on three more runs down the stretch against Shields and his bullpen.

“For my part it was good,” Butler said of the homer, “but it was a bad game as a team. That’s one of those games where you feel like you’ve got to win. You feel like you had the advantage.”

Part of the reason they felt that way is that they had Shields on the mound.

But instead of keeping his team in the game, the Royals’ ace allowed eight runs — seven of them earned — on 12 hits, a walk and a hit batter in 6 1/3 innings. It was the worst outing for Shields (3-3) since last September, when he allowed 10 runs in another start against Detroit.

“I threw some good pitches. That’s a good hitting ball club over there,” he said. “I wasn’t locating my pitches. I was getting behind in the count. I didn’t do my job out there, bottom line. I’ve got to do a better job of getting outs. It’s just one of those games.”

Meanwhile, Porcello (4-1) continued what has been the best start to a season in his career, giving up a sacrifice fly to Eric Hosmer, the homer to Butler and little else. Porcello allowed just four hits while striking out six without a walk.

“He’s been throwing the ball great all season long,” said Victor Martinez, who had a pair of doubles and drove in two runs. “He’s showing he’s young but he knows what he’s doing out there. He’s giving us a great chance to win ballgames.”

J.D. Martinez and Alex Avila also drove in two runs apiece as the Tigers won their fourth straight against the Royals.

As if that wasn’t bad enough for Kansas City, the club also lost All-Star catcher Salvador Perez when he fouled a pitch off his shin in the seventh inning. He was day to day with a bruise.

Shields first got into trouble in the second, when he loaded the bases but escaped the jam unscathed. But things only got worse in the third, when a single by Torii Hunter and back-to-back doubles by Miguel Cabrera and Victor Martinez gave Detroit a 2-1 lead.

They never gave it back the rest of the game.

J.D. Martinez kept the onslaught going when he led off the fourth with a double, and Avila followed by hitting the first pitch of his at-bat for his first homer of the season. Detroit added another run later in the inning when Andrew Romine reached third on an error by the Royals’ Mike Moustakas, and then scored on a double-play groundout.

Shields was finally pulled in the seventh, allowing another run and leaving the bases loaded while recording one out. Reliever Kelvin Herrera gave up a double to J.D. Martinez that brought in two more runs and gave the Tigers an 8-2 lead.

That was plenty of support for Porcello, who had been miserable in the month of April until this season, when he went 3-1 with a 3.96 ERA. He kept that momentum going against Kansas City, a team he oddly never faced last season, retiring his final 12 batters.