ARLINGTON, Texas -- Cody Bellinger was moved to designated hitter a little more than an hour before Game 4 of the World Series on Saturday because of stiffness in his lower back.

A.J. Pollock replaced Bellinger in center field against the Tampa Bay Rays.

Los Angeles Dodgers manager Dave Roberts, speaking to local reporters, said Bellinger received treatment at the ballpark and tried to move around but his back did not cooperate.

Roberts called Bellinger's back issue "a day-to-day thing" and said Bellinger would return to the outfield for Sunday's Game 5 if his back loosens up properly.

Bellinger is one of the best defensive center fielders in the game, a major benefit given the expansive outfield at Globe Life Field. Pollock came up as a center fielder but does not cover as much ground.

Roberts told reporters he considered moving Mookie Betts from right to center but decided otherwise because it would put multiple players out of position.