Wednesday night's game against the Los Angeles Angels was postponed by a steady rain that began during batting practice and escalated into heavy thunderstorms in the early evening.
The postponement was announced shortly after the 7:05 p.m. scheduled start. No makeup date was announced.
The Indians said Wednesday that Brantley, who leads the team with 11 homers and 46 RBIs while batting .323, has been diagnosed with a concussion and will likely be out of the lineup until Saturday.
Cleveland can't afford to be without Brantley, who is second in the majors with eight outfield assists, for very long. He sounded encouraged after participating in some activities Wednesday.
''I'm getting better every day,'' Brantley said. ''I played catch, hit off a tee and got a good workout in. It's all positive.''
The concussion was diagnosed when Brantley had tests Tuesday at the Cleveland Clinic. He was injured trying to break up a double play sliding into second base Monday.
''Michael is doing very well,'' manager Terry Francona said. ''Everything that has been introduced to him, the reaction tests, he's done very well.''
The team hopes to avoid placing Brantley on the seven-day concussion list.
''The doctors, trainers and Michael think that Saturday is realistic,'' Francona said. ''So as opposed to missing seven games, he could maybe miss five games.''
''I don't want to put a deadline on anything,'' Brantley said. ''My goal is get back out there as fast as possible.''
Brantley was removed from Monday's game and passed an initial concussion test, but was sent to the hospital after experiencing discomfort during his pregame routine Tuesday.
The Indians also hope the rainout will cool off the red-hot Mike Trout, who homered twice and had four RBIs in the Angels' 9-3 win Tuesday. Francona joked following the game that he would like to see Trout get a day off so the two-time All-Star didn't tire out.
Trout is batting .410 with eight homers and 26 RBIs over his last 22 games and has 14 RBIs in his last 13 games against Cleveland.
While Trout has been sizzling, designated hitter Raul Ibanez has struggled with a .153 average. Manager Mike Scioscia is sticking with the 42-year-old veteran.
''I think Raul hopefully is getting more comfortable in the box. He's had some good at-bats in this series,'' Scioscia said.
Ibanez is getting playing time because rookie C.J. Cron is also battling a slump and has only played once in the last week. The right-handed hitter is batting .275 this season, but is just 3 for his last 20 with seven strikeouts.
Since the teams conclude the series Thursday with a noon start, the decision was made to not play a doubleheader and the game will be made up on a mutual day off.
''It's never in anybody's best interest to play a doubleheader,'' Scioscia said.
Both teams will stick with Wednesday's scheduled starters for the series finale. Left-hander C.J. Wilson will pitch for the Angels against right-hander Justin Masterson.