PHILADELPHIA — Jacob deGrom threw his regularly scheduled bullpen Saturday and said he plans to throw his second on Sunday. The righthander is on track to make his next start after taking a line drive off of the back of his upper right arm.

“It was good and I will do it again tomorrow,” deGrom said after the workout at Citizens Bank Park.

DeGrom is scheduled to start the second game of the Subway Series, Tuesday night in the Bronx.

The Mets right hander had thrown 6.2 scoreless innings Thursday night when Nick Williams’ 99-mile an hour line drive came back and hit him on the back of his right-upper arm in the triceps area.

He was diagnosed with a contusion.

Ricky Bones was the lead negotiator. The Mets bullpen coach watched the ball land in the seats right next to the visitor’s bullpen at Citizens Bank Park and jumped into action.

“It was a Phillies fan,” Bones said of the fan who caught the ball on Amed Rosario’s first career home run. “I thought to myself he was going to be difficult, but he was very nice. He didn’t know it was Rosy’s first homer, but when we told him he gave it to us right away.

“It cost us three balls.”

The relievers put the ball aside, took another and wrote all over it and had clubhouse manager Kevin Kierst present it to him as a joke. The rookie tried to look thankful as he accepted the ball spoiled by the bullpens signatures. And then Kierst game him the pristine authenticated ball.

“We had to get Rosy his first home run ball,” reliever Erik Goeddel said.

“And we had to have a little fun with him first,” Bones said.

Chris Flexen will make his fourth major league start Sunday and it’s important for the 23-year old to build off his last start. Flexen allowed three runs on four hits in 5.2 innings work as the Mets beat the Rangers 5-4 at Citi Field.

“It’s all about command. In his first starts it was a lot of deep counts. Then, when he would miss, he’d miss over in the plate. I thought he had his best secondary pitches of the times he’s pitched up here so far,” Mets manager Terry Collins said. ” You need those in the big leagues. You need to be able to throw them when you are behind in count. These guys think you are throwing a fastball and they attack it, they hit it hard. You gotta keep hitters off guard and hitters away from strengths and I thought the last start was a huge step for him He has the stuff to pitch here.”

And the Mets, who have already shifted from the 2017 season to preparing for 2018, need him to show that. He needs to show the front office that he can be a guy they can call up in an emergency next season and that he can be a part of their team in the future.

“As we experienced this year, you never know what’s going to happen,” Collins said. “You want to have your name at top of list if something happens. You are guy that can replace someone if they go down. Especially, this month, I always look at this month more than September. In September you face teams with a lot of young players, you’re not playing playoff teams, it’s really tough to really judge them. The month of August is very important. If (the young players) finish strong this month, I think it will be a real big step as we head into the off season.