The right adductor injury sustained by U.S. men's national team goalkeeper Tim Howard is more severe than first thought, according to a source with knowledge of the situation.

The source told ESPN FC the injury will require a recovery time measured in "months, not weeks," and such a timeline would render the Colorado Rapids goalkeeper unavailable for the remainder of the MLS playoffs.

The U.S. Soccer Federation released a statement Sunday indicating that Howard had suffered a right adductor injury during the first half of Friday's 2-1 World Cup qualifying loss to Mexico.

He was forced to leave the match in the 40th minute, and was replaced by Brad Guzan. The statement also said Howard wouldn't be available for Tuesday's World Cup qualifier against Costa Rica, and that Howard had returned to Colorado "for further evaluation and to determine treatment plans."

The source added that those plans may involve surgery, and that Howard's recovery time may extend into the start of preseason, which is set to take place in late January.

Tim Howard could not finish Friday's match against Mexico because of injury. USA Today

The injury is a significant blow to the Rapids' quest to win their second MLS Cup title. Howard was the hero in Colorado's penalty shootout defeat of the LA Galaxy in the Western Conference semifinals.

Colorado will play the Seattle Sounders in the Western Conference finals, with the first of the two legs slated for Nov. 22.

The Rapids will now turn to Zac MacMath to take Howard's place in goal. MacMath had been the starter prior to Howard's arrival in July, and put up impressive numbers, including a goals-against average of 0.76 in 17 matches.