The injury has been bothering Sizemore for about a week and he had been considering not playing in the WBC. He was scheduled to leave training camp with Indians third baseman Mark DeRosa on Sunday and join the American team in Clearwater, Fla.
Sizemore played in the Indians' first two Cactus League games. His leg bothered him, even though he stole a base Thursday.
"I wasn't able to get through either game without pain," said Sizemore, who injured the groin taking fly balls about a week ago.
Sizemore batted .268 with 33 homers, 90 RBIs and 38 steals last season. He and Detroit's Curtis Granderson were expected to share center field for Team USA.
Sizemore, who always opposes manager Eric Wedge's attempts to give him a day off during the season, couldn't hide his disappointment over missing the WBC.
"This was something I was looking forward to," he said. "I was excited to get a chance to play for my country."
Sizemore discussed the situation with Wedge and members of the team's training staff Thursday night. He told Wedge on Friday morning that he thought it was best he remain in camp.
"We talked about it," Sizemore said. "I slept on it. I was pretty sure what I was going to do, but I wanted to give it one more day. I'm not doing them any good if I show up with an injury. I'm not doing my team any good if I leave for three weeks and battle through an injury and I'm still hurt when I come back."
Sizemore won't play in any exhibition games for a few days.
"I feel bad for Grady," Wedge said. "I know how important it was for him to play. I know how conflicted he is right now. Grady always wants to do right by everybody. In the end, he felt like he wasn't doing anybody any good by going out there and playing, risking the fact he's not going to be healthy and making the injury potentially worse."
Indians general manager Mark Shapiro and assistant GM Chris Antonetti called Bob Watson, the GM of Team USA on Friday morning. Wedge also planned on calling USA manager Davey Johnson.
"Bob was very understanding," Wedge said.
Wedge doesn't think Sizemore's injury will be a long-term issue.
"Obviously, we have enough time in camp where we can give him the time he needs," Wedge said.
Earlier in camp, Wedge expressed concern about losing some of his players to the WBC, which will run from March 5-23. DeRosa (USA), outfielder Shin-Soo Choo (South Korea) and reliever Rafael Perez (Dominican Republic) are scheduled to participate in the international tournament. The Indians have minor leaguers who will be playing as well.
"I think it's tough on the players timing-wise," Wedge said. "But I don't think anybody has a good solution to when a good time is to do it. I don't know. I don't have an answer. I think they tried to make it a little later this time and I think that is a good thing. It's a great promotion of baseball. It's great for international baseball. It's patriotic for everybody, regardless of where you're from. But I think it is tough on the players physically."
In recent weeks other players have wrestled with decisions to play in the WBC or stay with their major league teams.
Wedge worried about players getting hurt in the WBC or missing valuable time to get ready for the upcoming season.
"I think everyone is concerned about the physical part, especially with pitchers," Wedge said. "From my standpoint, I worry about the position players who aren't going to play because you are losing two or three weeks of preparation. I don't know how much practicing is going on over there. It's something we have to keep an eye on."