The one-out reliever will have had a longer run than baseball’s pitch clock, but both are being virtually eliminated in a series of rule changes introduced by Major League Baseball and the Players Association.

MLB announced Thursday that, starting in 2020, the active roster will increase from 25 to 26 players, and that all pitchers must pitch to a minimum of three batters or the end of a half-inning before being relieved. The minimum placement period for the injured list, formerly known as the disabled list, will increase from 10 to 15 days, and rosters will expand in September to just 28 players instead of 40.

The league hopes that limiting pitching changes can improve the pace of play, since last season was the seventh-straight year that games averaged at least three hours. Limiting rosters in September will keep substitutions at a minimum. Bryce Harper joked last week that Gabe Kapler made so many changes last season against the Nationals that the slugger questioned whether he wanted to play for the Phillies manager.

“They had like 45 guys or whatever they had in the clubhouse, switch this guy, switch that guy, and our game was like 5 1/2 hours, so it was kind of tough to be able to go, ‘Oh yeah, I like this guy.’ But no, he’s great,” Harper said.

The league and union both said they will meet and discuss a renegotiation and extension of the basic agreement, which is set to expire after the 2021 season.

For this season, the league agreed to not implement the pitch timer that was introduced this spring, and it eliminated August waiver trades, choosing to have just the July 31 trade deadline. League officials shortened inning breaks by five seconds and reduced mound visits from six to five.

MLB also altered the All-Star Game voting process by having a “primary round,” in which fans vote for players, with the top three vote-getters at each position moving on to an “election day.” The winners of a one-day runoff will then be deemed All-Star starters. And the winner of the Home-Run Derby will get $1 million.

Arrieta’s struggles

Jake Arrieta struggled on Thursday, allowing five runs on six hits in a laborious 3 1/3 innings. The right-hander took solace in the fact that he threw 65 pitches, which he said was the goal of his third start of the spring.

“I’m not going to cry about it,” Arrieta said. “I’m not going to watch video of it at all. Didn’t feel great. I would have liked better results. It didn’t happen that way. Move on, that’s it.”

Arrieta allowed two homers, including one to his first batter. He will make two more starts before starting one of the team’s first three games of the regular season against the Braves.

“I felt like I was gator-arming it, not getting extended,” Arrieta said. “Just one of those spring training days where it didn’t sync up quite the way I wanted.”

Extra bases

Cesar Hernandez started at second base, playing in his first Grapefruit League game in two weeks. He said he felt good after being out with a hip-flexor strain and will be ready for opening day. ... Andrew Knapp “solidified his position” and remains the favorite to be the backup catcher, Kapler said. ... Drew Anderson pitched four scoreless innings in a 4-3 split-squad win over Tampa Bay in Port Charlotte. The right-hander is a dark horse to crack the starting rotation. ... Nick Pivetta will start Friday against Toronto, Aaron Nola will start Saturday against Houston, and Jerad Eickhoff will start Sunday against the Yankees.