On paper, Seth Lugo landed on the 10-day disabled list on Tuesday with a shoulder impingement. But in reality, it’s his right elbow that has prompted his latest trip to the shelf, multiple sources told Newsday.

Lugo has been pitching through a partially torn ligament in his elbow suffered this spring, choosing to rehab rather than undergo Tommy John surgery which would have wiped out his season.

His shoulder issue, sources said, is believed to be relatively minor, and likely fallout from pitching through his elbow condition. Lugo described a lingering pinching sensation in his shoulder, which will be reevaluated after rest.

But Lugo, 27, downplayed worry about his elbow and any talk about surgery. He also insisting that doctors told him the conditions are not related. But manager Terry Collins said he is concerned that the shoulder issue might be linked.

“I know that if it’s not the elbow, that it always concerns me that you’re changing your delivery to compensate because you’ve got a bad elbow and all of a sudden it’s your shoulder,” Collins said. “I know one thing: I don’t like to hear shoulder problems. Those scare you more than anything.”

Lugo had been slated to start Wednesday’s Subway Series game against the Yankees. Instead, the assignment will fall to righthander Robert Gsellman, who will be activated from the disabled list.

Since coming off the disabled list in June, Lugo hasn’t complained of pain. But a source said he has been working in a somewhat diminished state, unable to generate the same arm speed as he had before the injury.

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The numbers seem to bear that out. Lugo has seen an across-the-board dip in velocity. The spin rate on his curveball — the pitch that helped him bail out a banged-up rotation last year — — has also seen a noticeable drop. But Lugo chalked that up to a different mental approach rather than a physical issue.

“For me, when I was younger in years past, I could reach back and try to overthrow one and blow it by somebody,” he said. “But with the elbow, I’m more just trying to play it smart, just execute the pitch and not try to overdo it. I think it’s not so much a physical reason that the velocity is down. I think it’s just me being conscious and being smart and taking care of the elbow.”

In 12 games (11 starts), Lugo is 5-3 with a 4.85 ERA in 68 2⁄3 innings. He hasn’t been as effective as he was last season, when he went 5-2 with a 2.67 ERA while emerging as a stabilizing force for a starting rotation that wilted beneath the weight of injuries.

Lugo, 27, suffered the injury sometime during the spring. Pitching through partial UCL tears isn’t uncommon, with the Yankees’ Masahiro Tanaka and the Cardinals’ Adam Wainwright as prominent examples.

Said Lugo: “Surgery is not even a thought.”

Yet, Lugo has been pitching with a partially torn ligament. And Tommy John surgery has always loomed as a possibility, with this latest setback potentially increasing the likelihood of the procedure.

For now, Gsellman will rejoin the rotation. In 17 games this season (14 starts), Gsellman is 5-5 with a 6.15 ERA in 76 innings.

He struggled early during his minor-league rehab assignment, prompting GM Sandy Alderson to say that performance rather than health was the reason he had yet to be promoted to the big leagues.

Indeed, Gsellman responded by tossing six shutout innings on Friday for Double-A Binghamton. He threw 83 pitches in that outing, which should allow him to take the mound on Wednesday with minimal pitch-out restrictions.

When asked about Alderson’s comments, Gsellman responded simply: “I don’t really care.”