Angels left-hander Hector Santiago is hoping his luck will change

Hector Santiago will start against Houston on Tuesday night, the second day of the summer. He did the same thing one season ago and lowered his earned-run average to 2.68.

It’s nearly twice that this year, at 5.30. What has gone wrong?

“A lot of things,” Santiago said. “A lot more walks. Some missed calls from the umpires that could’ve changed things. I think everything was going wrong, basically.”

One big thing: In the first half of 2015, the left-hander benefited from a remarkable stretch when nearly 90% of baserunners he let on did not score. This year, about a third of his baserunners have scored.

“There’s no doubt it’s all luck,” he said. “When a guy swings a bat, he can miss it by an inch or he can square it up perfect, and it’s luck. Everybody has luck involved. And, right now, it’s not going my way. I think it’s a matter of just throwing more strikes and consistently being ahead in counts.”

Santiago’s velocity has fluctuated wildly. His average velocity in his final May start was 5 mph faster than in his first start of the month. Santiago thinks it is a product of his troubles throwing strikes: He cannot focus on throwing to his maximum capacity when he is behind in counts.

He seems somewhat insulated, but one member of the Angels’ starting rotation may soon depart, as Nick Tropeano will throw five innings on rehab assignment for Class-A Inland Empire on Thursday. He has been on the disabled list since June 4 because of what the team termed shoulder tightness.

Angels Manager Mike Scioscia said Tropeano could rejoin the big league rotation for his next start or make another in the minors. He declined to confirm whether the club has had internal discussions about which pitcher would lose his spot when Tropeano returns. He also was unwilling to confirm Tropeano would have a spot when healthy.

“We’ve got a ways to go before we are going to make a decision,” Scioscia said. “Let’s just wait and see where Nick is, and then we’ll make a decision based on our evaluation.”

Short hops

The Angels have planned to give Albert Pujols games off on multiple occasions this season and then nixed the plan when Pujols reported feeling great after pregame workouts, Scioscia said Monday. Pujols carried a .703 on-base-plus-slugging percentage into play Monday, the worst mark of his career. … Scioscia said infielder Cliff Pennington is still “a ways away” from returning to the roster. He spent the weekend rehabbing his strained left hamstring in Arizona. … Left-hander Tyler Skaggs will throw four innings in an extended spring training game Wednesday in Arizona. Skaggs last pitched to hitters June 8.

pedro.moura@latimes.com

Twitter: @pedromoura