The Atlanta Hawks, one of the three teams in the East with a winning record, suffered a major blow to their campaign on Friday when an MRI showed that forward Al Horford completely tore his right pectoral muscle during the team's double-overtime triumph over the Cleveland Cavaliers last Thursday. The injury will keep the franchise star out indefinitely.

It is still uncertain if Horford will undergo surgery. In 2012, he suffered a left pectoral muscle injury that kept him in sickbay for four months.

"We will work with Al and complete our due diligence to determine the next best steps," Hawks general manger Danny Ferry said in a statement as quoted by ESPN.com. "Injuries are part of the challenge of an NBA season."

Horford left the game during the first overtime and did not return. The team said the MRI was conducted by Dr. Michael Bernot in Atlanta.

He is the team's leading scorer (18.6) and rebounder (8.4) this season, one of only six players in the league to do so. The others are LeBron James of the Miami Heat, Kevin Love of the Minnesota Timberwolves,Carmelo Anthony of the New York Knicks, LaMarcus Aldridge of the Portland Trail Blazers and DeMarcus Cousins of the Sacramento Kings.

His absence leaves a huge hole on the Hawks' offense. The team may have to make do with seldom-used center Pero Antic to fill Horford's role. While the Hawks have been playing well with a 16-13 record, good for third place in the East, it remains to be seen how much damage Horford's absence will do to the team's campaign.