Jim Salisbury of NBC Sports Philadelphia noted that Realmuto has been dealing with a bone bruise at the base of his left hand.
Realmuto had sat out the Phillies' past four games before finally getting placed on the IL. Gelb added that since an IL stint can only be backdated by three days Realmuto will have to miss at least a week.
The 30-year-old remains the best catcher in baseball, hitting .294 with four homers and 17 RBI in 35 games this season.
He has been excellent for the Phillies since joining in a trade ahead of the 2019 season, hitting career highs in homers (25) and RBI (83) that year before finishing the COVID-19 shortened 2020 campaign with a .266 batting average to go along with 11 dingers and 32 RBI in 47 games.
That offense, combined with his excellent coverage and throwing arm behind the plate, has made Realmuto a valuable part of a Phillies core that also includes Bryce Harper, Rhys Hoskins, Aaron Nola, Zack Wheeler and young third baseman Alec Bohm.
The team remains a threat to win the NL East and reach the postseason for the first time since 2011, but it will be hard to do so without a healthy Realmuto.
While he's out of action, look for Andrew Knapp to step into the starting catcher role, with Rafael Marchan likely to serve as the backup.
Neither Knapp nor Marchan will come anywhere close to providing the type of offensive output Realmuto does, as Knapp is hitting just .175 this season, while Marchan has appeared in just five career MLB games.