I doubt he absolutely "needs" the extra rest. More likely, the Brewers are simply exercising caution with their best player, in addition to realigning the rotation so that their "one-two punch" is back in order. It's a long season, and one that is not going to be determined by having Burnes start one game as opposed to two games this week. Finally, @Brock Beauchampwould probably be able to back me up on this, but the Twins have hit some elite pitchers such as Gerrit Cole and Shane McClanahan pretty hard this year, while having some struggles against lesser pitchers. Maybe the Brewers have noticed this and are willing to take their chance with a guy like Alexander against that lineup?