ATLANTA — Pat Neshek is concerned that the shoulder injury that landed him Friday on the disabled list could "be something serious."

The Phillies reliever said he started feeling discomfort a few days ago in the back of his right shoulder. Neshek is unsure how much time he will miss. He is eligible to return as early as next Friday. The Phillies will evaluate him again on Saturday. Neshek felt "a little bit different" after his final spring training game and still did not feel right after throwing a bullpen session. He said he has never dealt with an injury like this.

"And that's what's kind of weirding me out a little bit," Neshek said. "But it's something like, if I had to pitch today, I know I could. But I'm more worried about how it's going to progress over the next couple weeks."

The Phillies begin the season with Neshek and Tommy Hunter — the two free agents they signed in December — on the disabled list. They recalled righthander Yacksel Rios from triple A to fill Neshek's roster spot. Manager Gabe Kapler said the team has "a high degree of confidence" in the relievers they have.

"We have a strong level of belief and conviction that those guys can come in and get big outs for us, and we're not coming off that position for anything," Kapler said. "We have a lot of dudes out there."

Neshek learned an hour before opening day that he would be unavailable to pitch. He watched from the bullpen as five relievers failed to protect a five-run lead. The Phillies likely would have used Neshek in the eighth inning instead of Edubray Ramos, who allowed the tying run. It was terrible, Neshek said, to not be able to help.

"That happens, and you just feel like a bum at the end," Neshek said.

Selecting a catcher

Kapler said before Thursday's game that he envisioned Andrew Knapp and Jorge Alfaro splitting the catching duties for the first six games, but it was still surprising to see Knapp start Friday for the second game in a row.

Kapler plans out his lineups roughly a week in advance, and the catchers could be used in stretches instead of alternating between games. Kapler said the Phillies "love Alfaro, and we love Knapp" and said both are "perfectly capable" of handling themselves behind the plate.

"We're not picking and choosing necessarily between them every game. We're looking at a six- or seven-game stretch and how can we put them in the best position to succeed," Kapler said. "Who do they match up best against? We look at receiving. We look at blocking and throwing. We look at how they interact with our pitcher. We look at their offensive capability against the opposing pitcher. We have lots of conversations. We get all the information together, and we say, 'This is the right matchup for this stretch, and this is the right matchup for this stretch.'"

Extra bases

The Phillies opened the season with the youngest 25-man roster (average age of 26 years, 334 days old) in baseball, according to the Elias Sports Bureau. … Vince Velasquez will face righthander Brandon McCarthy in Saturday night's series finale. Carlos Santana is the only Phillies hitter with a more than three career at-bats against McCarthy and is 3 for 13 with a homer.