I found that it is mostly true , but the wording can be misleading. Emmanuel Clase, a pitcher for the Cleveland Guardians, was charged by federal prosecutors for allegedly helping bettors manipulate individual pitches. However, he has not been found guilty, so it is important to describe the pitch-rigging as an allegation rather than a proven fact.
The Department of Justice was the most important primary source I found. It confirmed that Emmanuel Clase was indicted and explained that prosecutors accused him of working with sports bettors to manipulate pitches. The DOJ also stated that the charges are allegations and that Clase is presumed innocent unless he is proven guilty.
MLB confirmed that Clase was indicted and that the league was cooperating with federal investigators. MLB had also previously placed Clase on non-disciplinary leave while the sports-betting investigation was taking place.
ESPN also reported that Clase and another MLB pitcher were charged in connection with an alleged sports betting scheme. This source helped confirm the information from the primary sources.
Reuters reported on the allegations against Clase and explained that prosecutors believe he manipulated pitches to help bettors. It also reported that Clase pleaded not guilty, which is important because being accused does not automatically mean someone is guilty.