MLB opened an investigation Monday into allegations that former Los Angeles Angels infielder David Fletcher gambled with an illegal bookie, an MLB source told ESPN, but investigators face a significant hurdle at the start -- where they're going to get evidence.

ESPN reported Friday that Fletcher, who is currently playing for the Atlanta Braves' Triple-A affiliate, bet on sports -- but not baseball -- with Mathew Bowyer, the Southern California bookmaker who took wagers from Shohei Ohtani's longtime interpreter, Ippei Mizuhara.

Fletcher's close friend Colby Schultz, a former minor leaguer, also bet with Bowyer and wagered on baseball, including on Angels games that Fletcher played in while he was on the team, according to sources.

"Government cooperation will be crucial in a case like this where we don't have evidence," the MLB source said.

MLB investigators will request an interview with Fletcher at some point, but he has the right to refuse cooperation if he can claim he could be the subject of a criminal investigation.

Fletcher did not respond to multiple requests for comment Friday.

The source declined to say whether MLB has reached out to law enforcement for assistance yet, but investigators are expected to do so.

Fletcher might continue playing during the MLB investigation, according to the source. He went 0-3 with a walk Saturday for the Gwinnett Stripers, the day after ESPN's report, and made a rare relief pitching appearance in Sunday's game, giving up three runs in 1 innings. Fletcher had never pitched professionally before this season, but has made three relief appearances for Gwinnett.

MLB sources have said that if a player bet illegally but not on baseball, it's likely he would receive a fine rather than a suspension. Any player connected to any betting on baseball games could face up to a lifetime ban.

Fletcher told ESPN in March that he was present at the 2021 poker game in San Diego where Mizuhara first met Bowyer. Fletcher said he never placed a bet himself with Bowyer's organization.