OAKLAND – Right-handed relief pitcher Michael Kelly was one of five players suspended by Major League Baseball on Tuesday for gambling on the sport, news that stunned his Oakland A’s teammates and forced the team’s front office to fill another hole in an already taxed and shorthanded bullpen.

In baseball’s biggest betting scandal in over 30 years, Kelly was one of four players suspended for a year by MLB with a fifth, San Diego Padres infielder Tucupita Marcano, banned for life for betting on baseball games.

Major League Rule 21, posted in every team’s clubhouse, states that gambling on any baseball game in which a player, umpire, league official, or team employee has no duty to perform results in a one-year suspension. Anyone who bets on games they have a duty to perform in receives a lifetime ban.

“If these guys have made bets on baseball, the rule’s pretty black and white,” A’s manager Mark Kotsay said Tuesday at the Coliseum before his team played the Mariners. “Baseball has made their statement, they’ve done their investigations, and now it’s time to turn the page.”

According to MLB, Kelly, 31, was found to have placed 10 bets involving nine major-league games as a member of Houston Astros’ Triple-A affiliate from Oct. 5-17, 2021. His bets included ones on game outcomes, over/under bets on the number of runs scored, and on an individual pitcher’s strikeout total. Three games involved the Astros.

Kelly’s account wagered $99.22 total and won $28.30. Despite the small amount of money wagered by Kelly, his gambling activity violated the rule in place and triggered that one-year ban.

Pitchers Jay Groome of San Diego and Andrew Saalfrank of Arizona and Philadelphia infielder José Rodríguez were also banned for a year. Like Kelly, those three players wagered under $1,000.

Marcano is the first active big league player to be banned for life for gambling since New York Giants outfielder Jimmy O’Connell in 1924. Pete Rose, baseball’s career hits leader, agreed to a lifetime ban in 1989 after an investigation concluded he bet on Cincinnati Reds games as he managed the team.

Several A’s players said there should be no ambiguity about baseball’s rules on gambling, with starter Paul Blackburn saying MLB does a good job of educating players about what is outlawed.

“Every single training, we have meetings about it with MLB security … and they kind of lay out the rules and just the structure of everything. There is no wiggle room,” Blackburn said. “If it’s something that could possibly put your career in jeopardy, then you might want to think twice about it.”

Kotsay learned of Kelly’s suspension from general manager David Forst on Monday afternoon. Kotsay said he then spoke briefly to Kelly about MLB’s discovery, which came after it received a tip in March about the betting activity by a legal sports betting operator.

Kotsay said his talk with Kelly was brief and cordial.

“I don’t know how he feels. We didn’t get into depth on the conversation,” Kotsay said. “In terms of betting on baseball, we know that the rule states that if you bet on baseball, there’s consequences.”

Kelly was selected off waivers by the A’s from the Cleveland Guardians last November and signed to a one-year, $740,000 contract. So far this season, he had pitched 31 1/3 innings, making him one of baseball’s most-used relievers.

In 28 appearances, the eighth-highest total in MLB, Kelly was 3-2 with a 2.59 ERA with 22 strikeouts and 10 walks. His last outing with the A’s came on Saturday in Atlanta as he pitched a scoreless inning and earned the win in what became an 11-9 victory over the Braves at Truist Park.

Entering this week, Kelly had not allowed an earned run in 10 of his last 11 games, sporting an 0.87 ERA in his last 10.1 innings. Remarkably, he had a 1.08 ERA (two earned runs in 16.2 innings) in 16 outings on zero or one day of rest.

“It just kind of sucks,” Blackburn said of Kelly’s suspension. “Just for how he’s been throwing for us and what he’s meant to that bullpen down there.”

With Kelly suspended and Brady Basso optioned on Sunday, the A’s reinstated left-hander Sean Newcomb from the 60-day injured list and selected right-hander Vinny Nittoli, a Livermore native whose family moved to Pittsburgh when he was 14, from Triple-A Las Vegas.

To clear a spot on the 40-man roster, Blackburn was transferred to the 60-day IL. Righty Aaron Brooks, designated for assignment on Sunday, was outrighted to Las Vegas.

Kotsay said Nittoli will move directly into a bullpen role, and Newcomb could be used in long relief if necessary. The A’s are already missing injured relievers Lucas Erceg and Kyle Muller.

Nittoli, who played with Kelly with the Phillies in 2022, said he was shocked by the suspension.

“He’s one of the greater teammates I’ve ever had,” Nittoli said of Kelly. “Great guy. I feel really bad for him. Not exactly sure everything that went down with it. Just finding out like everyone else. I feel bad for him.”

Can Kelly resume his MLB career once his suspension ends? He’ll only be 32 in June 2025, and as he’s shown this season, he can be effective at this level.

“His slider was working for him the best,” A’s catcher Kyle McCann said of Kelly. “He’s got (a 96 mph fastball) in the tank, too. So when you’re throwing a lot of sliders and can sneak in a heater like that, I think that made him very effective.”

“There’s an opportunity with the year that he had for Michael to have that chance to pitch in the big leagues,” Kotsay said. “We will have to see what happens when that decision needs to be made when he has the opportunity to come off of a suspension.

“I do believe in people being given a second chance in this situation. That’s up to Michael when he gets there to cross that bridge.”

The Associated Press contributed to this story.