LOS ANGELES - Aaron Nola will remain on the disabled list after he felt discomfort in his back Friday afternoon following a bullpen session at Dodger Stadium.

The Phillies were hopeful that Nola would have been able to start Monday at Wrigley Field, when the pitcher was eligible to be activated from the 10-day disabled list. But those hopes seemed unlikely, and it is not a surprise that Nola will miss more than one start with his lower-back strain. Manager Pete Mackanin said Nola was "improving, but he's not 100 percent."

"A couple days ago he said he felt great and then yesterday not so great," Mackanin said. "We're being cautious with him this early in the season."

Nola's rotation spot is being filled by Nick Pivetta, who will start Sunday against the Dodgers. Mackanin said Pivetta could have more than one start as the Phillies wait to reevaluate Nola. Pivetta, who was acquired in 2015 from Washington for Jonathan Papelbon, had a 0.95 ERA this season in three starts at triple-A Lehigh Valley.

Pivetta was originally slated to start April 26, but the previous game was rained out, so Pivetta's debut was pushed back. He last pitched April 20. It's been a long wait.

"The days have gone by really, really slow. It hasn't been a fast thing," Pivetta said. "I'm happy that I'm throwing a day game [Sunday] because I'll be able to wake up, and I'll be on the mound. There's not a lot of sitting around and waiting."

Pivetta, 24, pushed himself onto the Phillies' radar thanks to an improved fastball. He seemed to be just another pitcher before having a 2.59 ERA last season in his final 16 starts between double A and triple A. He started this season back at triple A and forced his way to the majors with a dominant start.

"Right now, it's nice. I'm calm and easy," Pivetta said. "But I'm sure when I get out there it will be a lot different. There's going be a lot more emotions. I'm going to try and settle down as much as I can because I don't want the game to get away from me. I want to be like I've been here before."

Father-son duo

Mark Leiter Jr. made his major-league debut Friday against the Dodgers, and the Leiters joined Ruben Amaro Jr. and Ruben Amaro Sr. as the only father-son duo in franchise history.

Mark Leiter Sr. played for the Phillies in 1997 and 1998. The son, a righthanded pitcher, pitched a perfect seventh inning Friday. He grew up an avid Phillies fan and urged his father to take him to the playoff games in 2008. The second batter he faced on Friday night was Chase Utley, one of the heroes of that 2008 team. Leiter worked a fly-out for a pretty cool debut.

Extra bases

J.P. Crawford and Dylan Cozens, both of whom started with wicked slumps at triple A, may have had breakout games Saturday. Crawford went 2 for 4 with an RBI, and Cozens went 3 for 4 with three RBIs and a homer. . . . Pivetta will face lefthander Hyun-Jin Ryu in Sunday's series finale. . . . Cameron Rupp and Tommy Joseph, both of whom are both batting under .200, were out of Saturday's lineup but should return Sunday.

@matt_breen philly.com/philliesblog