Jones had three singles, two RBIs and a stolen base in his first three at-bats, ending the night 3-for-5 in a 19-12 loss to the Boston Red Sox. Mullins, 23, went 3-for-4 with two doubles, two RBIs and three runs scored.
Jones had started in center for Baltimore since his arrival in 2008. Jones has a minus-18 defensive runs saved this season, according to Baseball Info Solutions. That ranks 34th among MLB center fielders, and the last-place Orioles are ready to try someone younger and faster in the middle of the outfield.
Manager Buck Showalter called Jones "one of the great center fielders in Oriole history," but said the 13-year veteran has known for a while that the switch was coming.
"It had to be the right guy," Showalter said. "We think Cedric might be the right guy."
Mullins had his contract selected from Triple-A Norfolk and batted ninth in his big league debut.
This is not a one-day experiment.
"Adam will play right and Cedric will play center. That's the way I perceive it," Showalter said. "If something happens with Cedric, we'll see. If something happens with Adam, well, I hope nothing does."
He added: "This is about the future going forward."
Jones' contract expires after this season. The Orioles attempted to send him to another team before the July 31 non-waiver trade deadline, but Jones had the right of refusal and used it.
Now, he will play out the season in right field while helping Mullins adjust to playing center in the big leagues.
"Him being the team leader, he's been very supportive with me playing center field," Mullins said. "We've had a lot of contact about it and just guiding me through it."
Jones tweeted Friday afternoon that he was embracing the change.
End of an Era!!!! Embrace Change!!!!— 10 (@SimplyAJ10) August 10, 2018
Mullins was selected by Baltimore in the 13th round of the 2015 draft. He started the year with Double-A Bowie before moving up to Norfolk.
In 59 games with Norfolk, he hit .267 with five homers, 18 RBIs and 12 steals. Mullins also carried a .994 fielding percentage.
To make room for Mullins, the Orioles designated Danny Valencia for assignment -- yet another move to make the team younger. The 33-year-old Valencia was batting .263 with nine homers and 28 RBIs.
"I'd be surprised if he doesn't land with a contending club," Showalter said.