OAKLAND -- Just because Mike Trout is the most accomplished rookie in recent memory doesn't mean the outfielder is going all out for a birthday bash.

Tuesday marked Trout's 21st birthday, and he was just planning on going out to dinner with his parents to celebrate. While that age is a pretty big milestone for most people, Trout's a different case, already chasing Major League milestones in his first full big league season.

The birthday boy is just focused on baseball, and after a big game in the Angels' series opener against the A's on Monday, he has reason to celebrate that, too.

Trout entered Monday's game hitting just .190 in five games against Oakland, his lowest batting average vs. any opponent (more than 12 at-bats). The last time the Halos squared off with the A's, the rookie went 1-for-13 in three games at the Coliseum in late May.

But he bucked that trend in the Angels' 4-0 win on Monday. Trout reached base four times and recorded three steals, and one of his two hits was a two-out RBI single in the second inning.

"Last series, wasn't seeing the ball good," Trout said. "Jumping a little bit. Last night, just tried to stay up the middle, stay short, not try to do too much. Once you try to do too much, you start to foul pitches off that you should be hitting. I just tried to slow my swing down."

At this point in the season, Trout's exploits are no longer a surprise, but that doesn't mean his teammates don't still take notice. For example, reliever LaTroy Hawkins -- old enough to be the rookie's father, at 39 -- said he still has moments where he's amazed at what Trout's doing.

Despite Trout's lack of experience and still-young age, for Hawkins, he's already proved where he stands among the game's best.

"Numbers will speak for themselves," Hawkins said. "People say what they want, but at the end of the day, numbers speak. Can't change those, no matter how hard they try."

Trumbo negotiating tough stretch at the plate

OAKLAND -- It's been a good year for Mark Trumbo.

The left fielder has built on his breakout campaign of last season, making his first career All-Star team and improving his overall numbers. But he's currently fighting through perhaps his worst stretch of 2012.

Trumbo has just five hits in his last 32 at-bats (a .156 average) and also has just one home run in his last 15 games. Monday night's matchup against the A's was another frustrating one for the 26-year-old, as he went 0-for-4 with three strikeouts.

But while Angels manager Mike Scioscia acknowledged on Tuesday that Trumbo is going through a tough stretch, he doesn't see much of anything wrong with the outfielder's approach or swing.

"I think in this little thing you've seen, maybe just a very marginal amount of expanding, but nothing that's been flagrant," Scioscia said. "He's gotten some pitches to hit and he's just missed them."

It seems likely that nobody's taking the slump harder than Trumbo, who's always hard on himself. While that can be a negative if a player applies too much self-pressure, it can also provide the impetus for getting through stretches such as the one Trumbo's going through right now.

"He's very accountable. I think that's an asset," Scioscia said. "I don't think it's hard on himself, I just think he expects a lot out of his talent. He's not hard on himself to where he's tying himself up in knots. He expects himself to be the type of player that we saw last year and we're seeing this year."

Richards hurts knee during Minor League start

OAKLAND -- Though he currently resides in the Minor Leagues, 24-year-old right-hander Garrett Richards could still prove to be an important piece for the Angels going forward this season.

But the team received some potentially worrisome news when Richards was forced to leave his start on Monday for Triple-A Salt Lake after just three innings because of left knee soreness.

The right-hander tweaked his knee when running to cover first base, and was lifted as a precaution. The knee was feeling better after the game, but it remains to be seen how severe the injury is.

"When a pitcher has to come out of game, obviously there's a concern, but we'll wait until we get some more information to see exactly what's going on," Angels manager Mike Scioscia said on Tuesday.

Richards has had two stints with the Halos this season and was just sent down last Thursday so the team could add some bullpen help in the form of David Carpenter. He's an important option should one of the team's current starters have to miss a start, or if Ervin Santana continues to struggle enough to warrant his removal from the rotation.

Overall, Richards is 3-2 with a 4.33 ERA in nine big league starts and 10 total appearances this season.

Worth noting

• With Tuesday night's game against the A's, Mike Scioscia moved into a tie with Felipe Alou for 50th place in games managed all-time, at 2,055.

• Former Cardinals manager Tony La Russa was at Monday night's game and waited outside the Angels clubhouse afterward to meet with first baseman Albert Pujols, his star player in St. Louis.