The Mets said nighty-night to the Dark Knight.

Matt Harvey, once regarded as a premier pitcher who could have joined Tom Seaver and Dwight Gooden among the Mets' greats, refused a minor league assignment and will be designated for assignment Saturday.

The 29-year-old right-hander lost his spot in the rotation last month after four starts, and he had a 10.50 ERA in four relief appearances.

"It's the end of an era," Mets general manager Sandy Alderson said before Friday night's game against Colorado. "And I used that term in broad senses. Matt has been a cornerstone certainly of my tenure here, a tremendous prospect at the time I arrived, tremendous accomplishments during the course of my tenure here. And it's a very unfortunate, difficult conclusion."

New York had hoped Harvey would be willing to work at the team's minor league complex in Florida in an effort to regain form. Harvey refused.

"We feel Matt is a starter (and) needs to work on 4 pitches," his agent, Scott Boras said in a text message. "In the bullpen a pitcher tends to focus on 2 pitches to get back to the rotation."

After Harvey is designated, the Mets have seven days to trade him or release him. Because of Harvey's $5,625,000 salary, a trade may be difficult to work out unless the Mets agree to send cash as part of a deal. If Harvey is released, a team signing him would owe just a prorated share of the $545,000 minimum.

"Very pleased he is healthy and with more than needed MLB (velocity)," Boras wrote. "We have a lot of clay to work with to build the starter sculpture."

Harvey is 0-2 with a 7.00 ERA in four starts and four relief appearances, leaving him with a 34-37 record and 3.66 ERA in six major league seasons.

"We've tried to find some other solution over a fairly long period of time," said Alderson, who was hired by the Mets in October 2010. "This was a long time coming. This is not someone who hasn't pitched well recently. So I mean this is something we've tried to address, we've struggled with, we've wrestled with over two managerial regimes."

Harvey's Mets finale was in an 11-0 loss to Atlanta on Thursday. He relieved Jason Vargas with New York trailing 6-0 in the fifth inning and gave up Ozzie Albies' three-run homer in a five-run seventh. Booed as he walked off the mound, Harvey took a seat in the dugout and stared at Citi Field.

"The move to the bullpen was dramatic in itself," Alderson said. "So I think that at this point, pragmatism, realism far outweighed other considerations."

Harvey would have been eligible for free agency after this season. As a player with five years of major league service, he cannot be assigned to the minor leagues without his consent.

"We feel like we failed Matt Harvey," manager Mickey Callaway said. "Our job is to help every player in there, and it's not a good feeling when you can't."

Selected by the Mets with the seventh overall pick in the 2010 amateur draft, Harvey made his big league debut in July 2012 and became a major sports figure in New York — both at the ballpark and at Manhattan night spots. He was nicknamed the Dark Knight of Gotham after Sports Illustrated called him that in a cover story in May 2013.

He started the All-Star Game at Citi Field that July and was 9-5 with a 2.27 ERA when he tore an elbow ligament during a game against Detroit on Aug. 24. That led to Tommy John surgery on Oct. 22.

Harvey returned in 2015 and went 13-8 with a 2.27 ERA as the Mets reached the World Series for the first time since 2000. But he slumped to a 4-10 record with a 4.86 ERA the following year and had season-ending surgery on July 18, 2016, to correct thoracic outlet syndrome.

He was 6-13 with a 6.70 ERA last season, when he was sidelined from mid-June until September because of a stress injury to the scapula bone in his right shoulder. He was suspended for three days without pay in May for skipping a game following a late night on the town.

The New York Post reported this week that Harvey was out partying in Los Angeles the night before pitching in San Diego last weekend.

"Usually I get upset if a report is unexpected," Alderson said this week. "So I guess the short answer is no."