Angels’ Mark Trumbo becoming more selective at the plate

SEATTLE -- It was one at-bat in a season filled with 126 of them through Wednesday, but it spoke volumes for the strides Mark Trumbo has made in plate discipline.

With two on in the seventh inning at Texas on May 13, Rangers reliever Mark Lowe threw a 1-and-2 pitch an inch or two off the plate. Trumbo took it for ball two and eventually drew a walk to load the bases, extending a rally in which the Angels scored three runs to trim Texas’ lead to 10-5.

Howie Kendrick grounded out to end the inning, and the Rangers won, 13-6, but had Kendrick hit a grand slam, Trumbo’s walk would have set it up. Had it been 2011, the inning probably would have ended with a Trumbo strikeout or weakly hit ball.

“Last year, that was a guaranteed swing,” Trumbo said of the 1-2 pitch from Lowe. “This year, I checked off of it and drew the walk. My approach is different. I’m trying to be more selective.”

So far, so good. Trumbo finished second in American League rookie-of-the-year voting in 2011, when he hit .254 with a team-leading 29 home runs and 87 runs batted in, but he was heavily criticized for his .291 on-base percentage, primarily the result of his 120 strikeouts and 25 walks in 539 at-bats.

Trumbo entered Thursday night’s game against the Seattle Mariners with a team-leading .325 average and .388 OBP. He was tied for the lead with six homers and second with 19 RBIs. He has already walked 12 times, putting him on pace for 43.

According to https://www.fangraphs.com, Trumbo’s “O-swing” rating, which measures pitches outside the strike zone a player swings at, has dropped from 42.7% last season to 35.0%. His batting average on balls put in play has jumped from .279 in 2011 to .389, a strong indication he’s swinging at better pitches.

“I had some good numbers last season, but I understand my on-base percentage was a weakness,” Trumbo said. “I thought about it during the off-season. It was hard not to. Last year, my mind-set was to do more damage. With that, pitchers respect you more and start to nibble more. That’s led to taking more pitches.”

With Albert Pujols struggling, Kendrys Morales not hitting for much power, Vernon Wells hurt and Torii Hunter on the restricted list, Trumbo has been the Angels’ one reliable middle-of-the-order slugger.

Trumbo opened the season as a utility player, a guy Mike Scioscia spot-started at third base, designated hitter, right field and left field. But the manager acknowledged this week that Trumbo “has to play somewhere — there’s no doubt he’s made a huge statement.”

Trumbo has played mostly right field the last two weeks, but when Hunter returns, Trumbo will move to left field.

“It’s not just that he’s walking more, he’s getting into more hitting counts and not giving those counts back to the pitcher like he did last year, when he expanded the zone a bit,” Scioscia said. “That’s experience. That’s what you like to see.”

Short hops

Bolstered by the acquisition of Ernesto Frieri on May 3, an Angels bullpen that blew six of its first seven save opportunities in April entered Thursday with a 0.89 earned-run average (three runs in 30 1/3 innings) in the last 10 games. … Angels pitchers entered Thursday with a major league-leading six shutouts, and their starters had an American League-leading 3.42 ERA.

mike.digiovanna@latimes.com