ARLINGTON -- The Drew Smyly Experiment is over.

The Rangers on Thursday decided they simply couldn't carry an unsuccessful and unhappy pitcher any longer, even if it costs them $3.5 million. In a host of roster moves that may have set a single-day record for a franchise involving left-handed pitchers, the Rangers designated Smyly for assignment, optioned Joe Palumbo to Triple-A Nashville, recalled Kyle Bird and purchased the contract of Locke St. John to add to their bullpen.

As a result, right-hander Jesse Chavez, who pitched five innings Wednesday, will move into the starting rotation. Chavez has a 0.58 ERA since May 1 and has pitched eight innings over two outings in the last week. He should be capable of giving the Rangers 75-80 pitches when he starts Tuesday at Detroit.

He becomes the second guy to attempt to replace Smyly, who turned 30 a week ago and had a 7.90 ERA in nine outings as a starter. He failed to get through the fifth inning in seven of those, which put an immense burden on the bullpen.

The Rangers also tried to use an opener in front of Smyly with some middling success, but he was not in favor of the idea. He was finally moved to the bullpen two weeks ago after insisting he did not require an assignment to the injured list for a minor ankle sprain. While he pitched fairly effectively in a three-inning mop-up outing against Cincinnati over the weekend, earning a save in the process, he allowed back-to-back-to-back home runs in a relief stint against Cleveland on Tuesday.

"It was just a situation where we thought a fresh start for everybody might be best," Rangers general manager Jon Daniels said of Smyly.

Said manager Chris Woodward: "It was a tough situation. He was fighting to work things out, but it was probably best for him and for us to move on."

Smyly left the Rangers clubhouse without comment Thursday.

The Rangers traded for Smyly, who had been with the Chicago Cubs, this winter in what amounted to an exchange of financial obligations. The Rangers would have been obligated to pay the Cubs $6 million toward a contract buyout for Cole Hamels as part of a midseason 2018 trade. Instead, they took Smyly and his $7 million contract, creating a net extra outlay of $1 million.

Smyly had missed two seasons while recovering from Tommy John surgery before joining the Rangers. He simply never found any consistency.

As for Palumbo, the Rangers opted to change directions after watching Cleveland hitters tee off for seven runs. The club had intended to give Palumbo a longer look as a starter, but Cleveland's ability to hone in on his fastball and eliminate other pitches concerned the Rangers.

"I saw a team that was very prepared for him," Woodward said. "Like a Bill Belichick team, they seemed determined to take away his strength, his fastball, and they did that. He had a hard time commanding the curve ball and changeup. He tried to use them, but he couldn't land them and it allowed [Cleveland] to sit on the fastball even more. It's a learning lesson for him. I've seen it happen with a bunch of young pitchers."

Palumbo will go to Triple-A Nashville. So it amounts to a promotion by demotion. He had spent the season at Double-A Frisco. He has pitched only 69 total innings above Class A as a professional.

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He's a Locke: Locke St. John, who will become the ninth pitcher to make his major league debut for the Rangers this season when he enters a game, gives the club something they have not had all year: a pitcher who truly profiles as a situational lefty.

St. John changed his delivery to a sidearm slot before the 2017 season while in Detroit's minor league system, and the deceptiveness of his delivery has made him an absolute terror against lefties. He's faced 57 left-handed hitters this year at Double-A and Triple-A and struck out 27 of them (a 47.4% strikeout rate). He's held them to a .102/200/.204/.404 slash line. Though his fastball is just average in terms of velocity, he supplements it with a breaking ball and changeup.

The four lefties who had pitched in relief had a horrible time against lefties. They had allowed a .428 OBP for 165 plate appearances.

"He gives us a more traditional lefty on left-on-left mix," Daniels said. "He's just had success at every step along the way, and we felt he was most ready to help us."

Briefly: 3B Asdrubal Cabrera was ejected for arguing balls and strikes by home plate umpire Doug Eddings in the bottom of the sixth inning. He then performed an impressive toss of his batting gloves from the dugout all the way to the edge of the home plate circle. ... OF Leody Taveras, ranked No. 3 on The Dallas Morning News' list of top 10 Rangers prospects, was promoted to Double-A Frisco following the Carolina League All-Star game. Taveras had repeated advanced Class A this year but was hitting .294 with a .368 OBP.