Nick Tropeano becomes the Angels’ fifth injured starter

Experiencing unexplained shoulder issues, Nick Tropeano was scratched from his Saturday start at PNC Park and placed on the 15-day disabled list.

The Angels moved up right-hander Jhoulys Chacin to take Tropeano’s starting spot and called up right-handed reliever Deolis Guerra from triple-A Salt Lake to take the roster spot.

Tropeano used multitudes to describe what he is feeling — “irregularities,” “a little discomfort,” “more stiffness than anything,” and “nothing really serious.” He also acknowledged the source of those feelings is undiagnosed, and speculated it could be tendinitis.

“We don’t know what it is,” the 25-year-old right-hander said.

A Saturday morning MRI exam revealed no structural damage within his shoulder, both Tropeano and Angels Manager Mike Scioscia said. Tropeano said he felt fit to pitch soon. The Angels opted to make June 14 the soonest day he could pitch.

“I’d say this is more precautionary, putting me on the DL,” Tropeano said. “I just needed a couple days. Obviously, we couldn’t afford it.”

Tropeano said with “100%” certainty he will be ready to pitch when he is eligible to be activated.

“I feel good right now,” he said. “I feel like I can throw. I just gotta play it by ear and listen to the trainers.”

Tropeano threw his standard bullpen session between starts Wednesday with the tightness already noticeable.

“I thought maybe it’s one of those valleys that we go through as pitchers,” he said. “And then the stiffness was there. It wasn’t something I wanted to push. So, we thought, as a team, that it would be better to be on the precautionary side of things.”

Through 10 starts, Tropeano’s earned-run average stood at a superb 3.25. Although he has a propensity to walk batters, he had been a pleasant surprise. Now, he joined four Angels starting pitchers already sidelined because of arm injuries: right-hander Garrett Richards and left-handers Andrew Heaney, C.J. Wilson, and Tyler Skaggs.

The Angels will need a starting pitcher Tuesday in New York and do not have an obvious option within their organization. Tim Lincecum, on track to start that day for triple-A Salt Lake, is not a possibility, Scioscia said.

Scioscia floated the idea of a bullpen game, which the team tried unsuccessfully earlier this season.

Short hops

Scioscia said the report he received from Lincecum’s first triple-A start Thursday noted that the 31-year-old right-hander hit 93 mph with his fastball. Lincecum touched 91 mph once during his first start in extended spring training. Assistant hitting coach Paul Sorrento said he will cede No. 55 to Lincecum when he arrives in the majors. … Back in his home state of Pennsylvania, Scioscia reflected on his childhood dream of playing outside linebacker for Penn State. But, as a 190-pound high-school senior, he ran the 40-yard dash in 5.1 seconds, too slow to be considered.

pedro.moura@latimes.com

Twitter: @pedromoura