LOS ANGELES - Aaron Nola said his back injury is improving and he believes there is a chance that he could start later this week.

The Phillies pitcher, who has been sidelined with a lower back strain since April 20, will throw a bullpen session on Monday at Wrigley Field before the team opens a four-game series against the Cubs. Nola felt tightness in his back after throwing a bullpen session on Friday at Dodger Stadium.

General manager Matt Klentak said last week he was hopeful that Nola would miss just one or two starts when the Phillies placed him on the 10-day disabled list.

"It came back again. It's taking a little longer than I thought it would," Nola said. "I really didn't think it was a big issue. I don't think it's too much. It just kind of lasted a long time. Every day it feels a little better. I just have to stay on the right path and keep doing what the trainers have me doing."

Nola was replaced Sunday by righthander Nick Pivetta, who made his major-league debut. Nola has made three starts and has allowed eight earned runs in 16 innings. He originally thought his back tightness was caused by a muscle but is now unsure.

"It feels a little bit better than it did the day after" his last start, Nola said. "For sure. It's still kind of nagging."

Saturday's debacle

Hector Neris needed just 11 pitches Saturday night to blow a three-run lead in a stunning 6-5 loss to the Dodgers. The pitcher allowed homers to the first three batters he faced in the ninth: Yasiel Puig, Cody Bellinger, and Justin Turner. He was pulled after allowing a one-out single. The winning run scored against Joely Rodriguez when Maikel Franco misplayed a ball at third base. Pitching coach Bob McClure met with Neris on Sunday morning, urging him to throw his splitter more than he has. The righthander has gotten away from his electric pitch in favor of his fastball. He paid the price for it Saturday. The Phillies want his splitter to be his primary offering.

"It's one of the worst losses I've ever been associated with," said manager Pete Mackanin, who has been in professional baseball for 49 years. "The way we lost. The way they tied it. It was tough to take. A real letdown."

Rupp and Joseph

Cameron Rupp hopes he snapped out of his funk on Sunday by going 3 for 4 with a pair of ground-rule doubles. He entered Sunday batting just .180 in his first 50 at-bats.

"It's something I can build off of," Rupp said. "After my first at-bat, I kind of gave that one away, swinging at a couple pitches out of the zone. I got back to being myself, really getting a pitch I can handle. That's what I've got to be better at. I know I haven't done it until this point, but it's something I can move forward with."

Tommy Joseph, who batted seventh in front of Rupp, went 0 for 4 with a pair of strikeouts. His batting average dropped to .179. He was robbed of a hit in the seventh when Turner made a backhanded dive at third base. Manager Pete Mackanin said he might try Daniel Nava during the team's four-game series in Chicago.

"I know what he's thinking: He finally hits the ball hard and Turner makes a great play. But you've got to hit the ball hard two or three times a game if you want to hit," Mackanin said. "That's where he's trying to get to. He's a little frustrated right now. But he's going to keep going out there and getting opportunities."

Extra bases

Odubel Herrera's bat-flip in the ninth inning seemed ill-timed. The Phillies were still down two runs when Herrera homered with two outs. It didn't seem to be the time for styling. "I don't care about bat flips. I don't care about that," Mackanin said. … Vince Velasquez, Jeremy Hellickson, Jerad Eickhoff, and Zach Eflin will pitch for the Phillies at Wrigley. Brett Anderson, Jon Lester, Jake Arrieta, and John Lackey will pitch for the Cubs. Monday's weather forecast in Chicago does not look good.