ANAHEIM, CALIF. – Garrett Richards dominated another team to continue an outstanding month on the mound. Yohan Pino couldn't duplicate his successful major league debut last week. And it made for a long night for the Twins at Angels Stadium.

As if the 6-2 loss to the Angels on Wednesday wasn't enough, the Twins might have suffered another, more difficult blow.

Exciting rookie shortstop Danny Santana injured his left knee while running to second base on a double in the third inning.

"Hopefully everything is good,'' manager Ron Gardenhire said. "He's day to day; that's all we know. We'll see how he feels tomorrow morning.''

The Twins got off to good start when Oswaldo Arcia, who began the game in a 0-for-31 skid, put Minnesota ahead 1-0 with a home run to center field in the second inning. It came on a pitch from Richards that touched 97 miles per hour on the radar gun.

Richards, who threw one pitch 99 mph Wednesday, shut the Twins out for the next six innings.

"Richards threw the ball very well,'' Gardenhire said.

Meanwhile, Pino did not.

The righthander went seven strong innings in his debut last Thursday but couldn't finish off hitters Wednesday. He gave up three runs in the second on a sacrifice fly by Grant Green and a two-run double to right by Kole Calhoun. Albert Pujols opened the third with a single and advanced to third on Josh Hamilton's double to right.

Pujols scored on Erick Aybar's sacrifice fly, and Hamilton scored on Howie Kendrick's single to make it 5-1.

"He never had an easy inning out there. They fouled off a lot of pitches and gave him fits,'' Gardenhire said of Pino, who gave up five runs and seven hits in three innings.

Joe Mauer had two of the Twins' four hits off Richards, a single to center in the first and bloop single to left in the eighth.

In addition to a big fastball, Richards mixed in a slider and curve. He reached 96 on the gun into the eighth inning. He gave up two earned runs over 7 ⅓ innings to raise his ERA to 1.29 in June.

"Garrett's stuff is electric,'' Angels manager Mike Scioscia said.

Santana played in only his 23rd major league game on Wednesday, but he already might be an indispensable player in the Twins lineup. He gives them a dynamic leadoff hitter with blazing speed and the ability to drive the ball. His arm is powerful at short, and he's gifted enough to pass as a center fielder without a lot of experience out there.

So Santana hobbling into second base had to be unsettling to the Twins.

With one out, Santana served a soft liner to left-center and turned for second. Suddenly, he was skipping on one leg as he reached the bag. He bent over as Twins trainer Dave Pruemer and Gardenhire rushed to second.

"It twisted a little after I hit [first] base,'' Santana said. "This is the first time in my life [hurting it].''

Santana was replaced by Pedro Florimon.

The Twins began the trip with a three-man bench but hoped to make through to the end of the week, when they expect to get Trevor Plouffe and perhaps Eduardo Nunez back from the disabled list.

Now they'll likely play at least Thursday's game with a two-man bench.