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The Twins weren’t happy with home plate umpire Alan Porter’s strike zone at times on Thursday. When an Andrew Miller pitch in the seventh inning was called a strike, the bench chirped and even mild-mannered Joe Mauer stepped out of the batter’s box to glance at Porter.

An inning later, manager Paul Molitor was out of the game.

Catcher Jason Castro, who was on the wrong end of several borderline calls throughout the game, tried to check his swing in the eighth with two strikes on him. Porter immediately ruled that Castro did not check his swing, making it his third strikeout of the game. Castro couldn’t believe it, and Molitor popped out of the dugout and engaged Porter for a few seconds before being ejected.

“I thought there was some inconsistencies today, but probably not the difference in the game,” Molitor said. “I just felt on that particular check swing that it was close. I haven’t looked at it, but I think that’s a hard call for him to make if he is tracking the pitch.”

Porter should have asked for help?

“That’s what I thought he should have done,” Molitor said.

It was Molitor’s first ejection of the season and fifth of his career.

Eyes on Robert

Cuban outfielder Luis Robert on Thursday was declared a free agent and can sign with any team as soon as May 20. And the Twins are among the teams scouting him. Robert left the island in January, and the Twins were one of many clubs on hand earlier this month at his showcase in the Dominican Republic.

Robert, 19, is a righthanded hitter who can play center but will likely settle into a corner outfield spot. His ticket to the majors is his power bat, which is considered to be advanced for his age. He’s considered a first-round talent if he was in this year’s draft.

Four teams — the Cubs, Dodgers, Royals and Giants — won’t be in play to sign Robert because they are serving penalties for overspending their international bonus pool money in previous signing periods.

Once the May 20 window opens, teams have until June 15 — the end of the 2016-17 international signing period — to reach a deal with a team.

O’Rourke review

Lefthander Ryan O’Rourke’s spring training ended when he was diagnosed with a strained flexor pronator mass near his elbow. An MRI exam revealed no structural damage, so O’Rourke was told to start a throwing program once the inflammation and discomfort went away.

The problem is that the discomfort returns when he attempts to throw. So he was in town Thursday to meet with Twins doctors and come up with a plan of action — which likely means a second opinion and a second MRI.

“It’s just frustrating to me because if nothing is torn, then why does it still hurt?” he said. “That’s the issue we are facing right now.”

Etc.

• Because of the rainout on Wednesday, the Twins have pushed lefthander Adalberto Mejia back to Saturday against the Tigers. That means Kyle Gibson will pitch on Sunday with an extra day of rest. Gibson left spring training looking strong but is 0-2 with a 6.91 ERA through three starts. Opponents have batted .300 against with him with four home runs.

• Mauer’s double in the fourth inning on Thursday was his 100th at Target Field, the most by any player. But it also was his first extra-base hit in 83 plate appearances, going back to Sept. 9 of last season, when he homered off Cleveland’s Danny Salazar.