LOS ANGELES — In their first rivalry game of the season, the Dodgers sent a figurative brushback to the Giants.

They left Aaron Rowand in the worst shape of all.

The Giants' leadoff hitter and centerfielder sustained two small fractures to his left cheekbone and was diagnosed with a mild concussion after a fastball from Vicente Padilla knocked him to the dirt in the fifth inning Friday night.

Although Padilla is a headhunter by reputation, the Giants didn't read obvious intent and didn't retaliate in their 10-8 loss at Dodger Stadium.

The Giants entered their archrival's lair with the best record in the NL West, but the Dodgers dismissed them like pretenders to the throne. The Dodgers' potent lineup battered No. 5 starter Todd Wellemeyer while taking a 7-0 lead on Andre Ethier's grand slam in the second inning.

The Giants probably will have a new leadoff hitter today; club officials didn't immediately place Rowand on the disabled list, but it's a likely move.

Padilla's first-pitch fastball hit Rowand on the ear flap and glanced off his left cheekbone. He hit the dirt and stayed in a crouched position as trainers checked him, then he was escorted to the clubhouse.

Manager Bruce Bochy said Rowand was lucid when he left for Huntington Memorial Hospital in Pasadena; teammate Aubrey Huff said Rowand seemed OK as he sat and watched video of the plate appearance.

A few Giants privately wondered if Padilla (1-1) had a screw loose, but they couldn't rationalize any obvious intent. The pitch loaded the bases with one out while the Dodgers had a five-run lead; Edgar Renteria followed by lining into a double play to end the inning.

"You always wonder what the intent was, but in that situation, that's not a time a pitcher is going to hit somebody," Bochy said. "It doesn't mean you like it, or any ball up high. But it does happen in this game. It's a scary situation."

Padilla said his target was inside "and the pitch ran in on him. He was right on the plate. With that kind of lead, there was no reason for me to start a conflict."

The Giants did not look to even the score, although Wellemeyer (0-2) had brushed back Matt Kemp in the second inning after he hit a two-run home run in the first.

The Dodgers sent the strongest message on the scoreboard while reasserting the power structure with their archrivals.

Even though they are just 5-5 through 10 games, the Dodgers romped to a 46-26 record against NL West opponents last year while capturing their second consecutive division title; they've been to the playoffs four times since the Giants' last postseason appearance in 2003.

By and large, the Giants carried over the momentum from a well-played spring. But Wellemeyer seems to have left his good stuff somewhere between Scottsdale Stadium and Wickenberg. He trailed 3-0 after he faced three batters: Rafael Furcal drew a walk in front of back-to-back shots by Kemp and Ethier.

Wellemeyer wasn't shy about expressing dissatisfaction with plate umpire Dan Iassogna.

"When you throw a strike, you expect it to be strike," said Wellemeyer, adding he felt he struck out Furcal to start the game. "He played it off pretty good, backing off, but it wasn't even on the black. It was over the white of the plate.

"It makes a big difference when you strike out the leadoff hitter instead of a walk."

All three of Wellemeyer's walks crossed the plate, including two on Ethier's slam. Wellemeyer retired nine of 10 batters after the slam while working on his forkball, a pitch he recently added to his repertoire.

Bochy said he liked the way Wellemeyer regrouped. Even if the Giants were motivated to find another No. 5 starter, young left-hander Madison Bumgarner isn't a candidate after two rough starts at Triple-A Fresno (7 innings, 21 hits, 11 earned runs, 3 home runs).

The Giants' loss brought back memories of their 0-6 road trip to Dodger Stadium and San Diego's Petco Park to open their road schedule last season. But they might have flushed a few bad vibes in the ninth, when Eugenio Velez hit a three-run home run to make the score respectable.