D'Arnaud had an MRI on Monday in Milwaukee, Asst. GM John Ricco said. The doctors then sent him back to New York to have further tests done.
D’Arnaud was expected to return to the starting lineup on Tuesday against the Brewers.
He hyperextended his left elbow during Saturday’s loss to the Braves.
Johnny Monell has been called up to replace d'Arnaud. Since being returned to the minors at the end of May, Monell is hitting .360 with a .420 OBP, nine doubles, one home run and 19 RBI over 24 games.