Rick Porcello's promising start to the season came to an abrupt end against the relentless Texas Rangers.

Porcello allowed eight runs in the first inning and the Detroit Tigers went on to a 10-4 loss to Texas on Saturday in the first game of a doubleheader.

Hamilton hit a three-run homer in the first for the Rangers, who have won eight straight. Mike Napoli went deep for a fifth straight game.

The Rangers routed Detroit 10-3 on Thursday night in the first game of a four-game set. After a rainout Friday, they picked up right where they left off, sending 12 men to the plate in the first against Porcello (1-1).

"They're hot and they're aggressive and confident," Porcello said. "It's a tough one to swallow, because I was unable to come up with an answer."

Matt Harrison (3-0) allowed three runs and six hits in 7 2-3 innings. He struck out six.

Miguel Cabrera and Austin Jackson homered for the Tigers, who send Justin Verlander to the mound for the nightcap.

Texas third baseman Adrian Beltre left with a strained left hamstring after hitting a second-inning double. He's not expected to play for the rest of the weekend.

The Rangers improved their major league-best record to 12-2. They've scored 44 runs in their last four games, and this was the first time they allowed more than three during their winning streak.

"These guys are tough, and obviously they're hot," Detroit catcher Gerald Laird said. "But we've got Ver going right now and coming back tonight."

Texas is off to a 7-0 start on the road, and the Rangers' starting rotation is 10-0, both team records.

Porcello entered his start with a 1.84 ERA. It was 6.32 by the time he left. He allowed nine runs — eight earned — and 10 hits before being pulled with nobody out and two on in the second.

"I was the most disappointed one in the ballpark today. I know I can go out there and beat those guys and pitch well against them, and I wasn't able to do it today," Porcello said. "It was a poor effort."

Ian Kinsler and Elvis Andrus started the game with a single and a walk before Hamilton lifted a towering home run deep into the right-field seats, his sixth of the season.

After a single by Beltre, Michael Young hit a grounder to second baseman Brandon Inge. Beltre held up to avoid running into a tag, Inge threw wildly to first for an error and everybody was safe.

Nelson Cruz hit an RBI single, and with one out, Mitch Moreland's single drove in two more runs to make it 6-0.

Kinsler added a two-run triple for his second hit of the inning.

Cruz hit another RBI single in the second before Porcello was lifted. After finishing Thursday's game with 19 hits, the Rangers had 14 in the first four innings Saturday and ended up with 17.

"It's an awesome thing when we all get going like that," said outfielder David Murphy, one of eight Rangers with two hits. "We've got so many bats in our lineup that we're hard to beat if we keep hitting."

Harrison had allowed only one run in 17 innings this season before the fourth, when Jackson connected and Delmon Young hit an RBI double. The Texas left-hander departed with a man on in the eighth, and Cabrera hit a two-run homer off Koji Uehara.

Detroit's Duane Below, who relieved Porcello, pitched six scoreless innings, allowing four hits and striking out four.

Napoli's sixth homer of the year — all in the last five games — was a solo shot in the ninth.

NOTES: Detroit LHP Daniel Schlereth worked two innings, then was optioned to Triple-A Toledo. The Tigers purchased the contract of RHP Thad Weber from Toledo for the second game of the doubleheader. ... Porcello's eight earned runs matched a career worst, and this was the shortest start of his career. ... Beltre hasn't missed a game this season, but he spent time on the disabled list last year with a left hamstring strain and was limited to 124 games in 2011.