ANAHEIM -- John Lackey looked ready for prime time, but his support crew appeared more suited for a graveyard shift.

Specifically Scot Shields, who proved unable to match Lackey in style or substance and spoiled the right-handed starter's return from the disabled list due to a right triceps strain that has kept him of the rotation since Opening Day.

As season debuts go, it was nothing short of solid, but true success is measured in the win column, and that stat was neither bestowed on Lackey nor his ballclub as the Angels dropped a 6-1 loss to the White Sox on Wednesday night.

The decisive blow was delivered by Carlos Quentin, who crushed a 2-0 fastball to center in the eighth inning off Shields for a grand slam that broke open a 1-1 game.

"It is always tough when you lose a game late, but there are some important things we saw tonight, and one of those things is the way John threw the ball," manager Mike Scioscia said. "That is probably the one thing we'll take away tonight."

For Shields, the breakdown was not reflective of recent performance.

The right-handed reliever, who was fresh off a victory in Tuesday's 2-0 win over the White Sox, took his first loss of the year and allowed runs for just the fourth of 17 appearances this season.

Shields (2-1) allowed a leadoff hit to Juan Uribe and then a sharp ground ball by Orlando Cabrera to short that Erick Aybar fielded but threw away into the visitor's dugout. Shields intentionally walked A.J. Pierzynski before Quentin iced the game.

"He hit a pretty good poke for a home run," said Shields, who took the loss. "That wasn't that bad of a pitch, it was down in the zone. But I got down in the count where I couldn't control the at-bat."

The night indeed goes down as a loss, but getting Lackey back on the mound could prove to be a big boost for the Angels. The right-hander did nothing to point to the contrary.

The offense struggled against White Sox starter Jose Contreras (4-3), who limited the Angels to four hits and just a run-producing sac fly by Mike Napoli. But Lackey matched Contreras pitch for pitch and aside from a shaky opening, Lackey never looked the part of a pitcher who just weeks earlier was nursing a sore arm.

Lackey took a bead on the strike zone from the first pitch, opening with a strike to leadoff batter and former teammate Cabrera before the shortstop flared a ground ball that Maicer Izturis could not field at second. Pierzynski followed Cabrera's single with a soft liner to left for a base hit, and Quentin produced the game's first run with a single to center.

That was also the first of five RBIs on the night for Quentin, who matched a career single-game high.

But Lackey, who said he was ready for this start and did not feel any pain through his seven innings and 99 pitches, induced a double play ball out of Jermaine Dye and then struck out Jim Thome to end the threat and the inning.

Paul Konerko led off the second with a single, but Lackey found his rhythm and retired 14 of the next 15 batters. Only Pierzynski reached in that stretch, as the White Sox catcher walked in the third.

Lackey was treated to some outstanding defense along the way and in the outfield in particular, as Torii Hunter and Garret Anderson made fine running grabs.

Dye singled to lead off the seventh and reached third on Joe Crede's two-out double to put Lackey on the ropes, but he came back to challenge Nick Swisher and got a fly ball from the White Sox center fielder to end the threat.

Lackey won the ERA title in the American League last year and would have been the likely Opening Day starter this season had he not suffered an injury in Spring Training. But he doesn't warm to the idea of being the team's No. 1 starter.

"An ace means there is a sense of comfort and we've got a pretty good chance to win when that guy is on the mound," Lackey said. "It is hard to call myself that because we have too many good pitchers on this team. We have several guys that can be called that."

Lackey deferred to a staff that leads the AL in victories by a starting rotation with 21 and is paced by right-hander Ervin Santana and left-hander Joe Saunders, who are a combined 12-1.

With Kelvim Escobar still out on the DL, the Angels were expected to struggle, but the team has found itself out front on the AL West.

"It suggests the depth of our team. Santana and Saunders have been incredible," Lackey said. "I think we knew they had capability of doing that, but they stepped up and did it at a great time for our team."