He’s been placed on the 15-day injured list in a move that is retroactive to Thursday.
Alonso was hit on his left wrist by a 96 mph fastball from Charlie Morton and left Wednesday’s game against the Atlanta Braves. He returned to New York for further testing after initial X-rays revealed no fracture.
Alonso leads the majors with 22 home runs, the NL with 49 RBIs and is hitting .231.
In other Mets moves Friday, catcher Tomás Nido has been outrighted to Triple A, infielder Luis Guillorme and lefty Zach Muckenhirn have been recalled from Triple-A, and right-hander Stephen Nogosek has been designated for assignment.
The team also said reliever Edwin Uceta had surgery to repair a torn meniscus in his left knee. Uceta initially went on the IL in April with what the team called a sprained left ankle. He is expected to be out for at least an additional eight weeks.
New York had lost six straight heading into a three-game series at Pittsburgh that began Friday.
Information from The Associated Press was used in this report.
Mets say Pete Alonso has bone bruise, sprain of left wrist