Too many strikes, too many runs for Mark Leiter Jr.

NEW YORK — The Phillies have 15 active pitchers. Seven of them are rookies. Two others are in their second season. The oldest pitcher in the rotation is Mark Leiter Jr., a 2013 22nd-round pick who was not invited to big-league camp in spring training.

The final month will be full of growing pains. Leiter learned a lesson in Monday's 11-7 loss to the Mets when he threw 46 of his 63 pitches for strikes.

He threw too many of them over the plate.

"There definitely could have been something that I could've done a little differently," Leiter said. "Maybe a few more misses off the plate. Try to get them to chase some balls maybe. It's kind of funny sometimes: You don't throw enough strikes, sometimes you might throw too many."

The Phillies like Leiter, 26, as a possible swingman for 2018. His advantages are his sizable arsenal and his strike-throwing abilities. But he was too predictable. His gruesome start Monday raised his ERA to 4.74, almost a run higher than what it was entering the game.

Leiter had pitched at least five innings in his first six starts.

"These guys are all young," manager Pete Mackanin said. "You can't really expect them to pitch like seasoned major-league pitchers. They're going to make mistakes. They're going to have good outings and bad outings. We've seen Leiter have some great outings.

"Little by little, hopefully they learn from their mistakes and improve with their command."

Kevin Siegrist, the 47th player used by the Phillies this season, did not leave a good first impression. He retired one of the four batters he faced. He walked two. It was his first appearance in the majors since Aug. 3.

The waiver claim from St. Louis averaged a tick under 92 mph with his fastball. His velocity is down from previous seasons, when he was a force in the Cardinals bullpen. That prompted St. Louis to cut ties last week.

Siegrist, 28, is making $1.64 million in this, his first year of arbitration.

The Phillies are 88-103 on Labor Day since 1894, when it became a federal holiday. … Ben Lively will pitch Tuesday against Mets ace Jacob deGrom, who has a 3.43 ERA this season.