PHOENIX -- Just as the Padres’ offense is beginning to fire on all cylinders, the starting rotation feels shaky.

Before the Padres’ four-game winning streak was derailed in an 11-4 loss to the D-backs at Chase Field on Sunday afternoon, the club placed right-hander Joe Musgrove on the injured list with right elbow inflammation.

Musgrove said he began to throw his between-starts bullpen session on Saturday and something didn’t feel quite right, so they shut it down. The 31-year-old said it wasn’t much worse than the soreness he routinely deals with throughout the season, but the team decided a stint on the IL would allow the elbow to completely calm down.

“If we were in a different spot in the season,” Musgrove said, “I feel like if I had to go out there and pitch, I’d find a way to get it done. Right now, if I push through it and end up missing the rest of the year, that kind of hurts everybody around here. So you have to put your own feelings aside for a minute and look at what’s best for the group.”

Musgrove plans to resume throwing in a few days and doesn’t expect to miss more than the minimum 15 days required.

It has been a bumpy first month and change for Musgrove, who carries a 6.37 ERA over eight starts, but he is coming off an encouraging outing against the Reds on Wednesday.

“I’d love to stay in there,” he said. “I felt really good coming out of the last start, delivery-wise, mentality-wise. My stuff felt like it was kind of back to normal, so it’s frustrating to have to go out and sit for 15 days.”

Manager Mike Shildt isn’t at all worried that Musgrove’s rocky start or this setback will keep the right-hander from delivering the results we’re used to seeing.

“I’ve got recency bias and I’ve got history bias with Joe,” Shildt said. “Last start, he was really tremendous; he looked like Joe. And the history is the history. He’s really a quality pitcher for us and has been for years.”

Musgrove landing on the shelf was only the first blow to the Padres’ rotation on Sunday, as 27-year-old knuckleballer Matt Waldron just didn’t have it against the D-backs, allowing eight runs on eight hits and three walks over three-plus innings.

“From the start, [my knuckleball] wasn’t where I wanted it to be,” Waldron said. “That was my worst performance of the season, but there’s only one way forward.”

Waldron’s setback and the news of Musgrove landing on the IL come just as the Padres’ rotation was on one of its best stretches of the season -- a club-record five straight walkless starts by the rotation.

Things began to turn around for the unit when Yu Darvish came off the IL on Tuesday.

Darvish returned from a bout of neck stiffness with five scoreless innings against the Reds. Musgrove followed with his bounce-back start on Wednesday in that series finale. Dylan Cease spun a gem Friday in the opener against the D-backs, and Michael King tossed six scoreless innings on Saturday.

“Just like hitting is contagious, pitching is contagious,” King said after his start. “Obviously, having Darvish come back and dominating his first one back from the IL set the tone for the rotation, and it just carried on from Joe to Dylan and then to me.”

That momentum took a little bit of a hit in the finale, as the Padres missed out on their first sweep of the season, but Shildt was quick to point out that the rocky finish doesn’t take away from a really good trip to Chase Field. Led by huge nights from Fernando Tatis Jr. on Friday and Luis Arraez in his Padres debut on Saturday, San Diego left Arizona with a series win.

Darvish returns to the mound Monday at Wrigley Field, looking to ignite another hot streak for the starting five. It seems like the offense will be there day in and day out, so the burden will fall to the rotation to make it count.

“If you get quality starts, you get a chance to compete,” Shildt said. “If you’re having trouble getting them, you put your club in a more compromised position.”