Rajon Rondo was a late scratch on Sunday’s Miami Heat/Boston Celtics contest because of a hyperextended knee. But there is fear that it could be worse. Much worse.

Here’s David Baumann from NBC Sports and Sportstalk 1080 from Florida.

Solid #NBA source tells me the Boston @celtics are fearing a possible torn ACL for Rajon #Rondo. Results from MRI coming soon. Updates ASAP.

— David Baumann (@DavidBaumann33) January 27, 2013

We’ll eagerly await the results. Rondo tweaked his knee on Friday night’s game against the Hawks. That game went to double overtime after Boston blew a 27-point lead; the Celtics would go on to lose by double digits. Rondo played nearly 45 minutes in that game so it seemed everything was fine. But when Rondo tried to warm up for Sunday’s game, there was no improvement shown so he was taken to New England Baptist Hospital for a precautionary MRI.

The Celtics are in a tailspin, having lost six in a row. Losing Rondo would be a huge blow for their playoff hopes. They’re currently hanging on to the eighth spot in the playoffs at 20-23, and only two games ahead of the Philadelphia 76ers.

Boston has been trying to keep this run as long as possible. Even when Ray Allen departed for the Miami Heat, they tried to fill in the gaps with a surplus of guards that included Jason Terry (who last played in the Dallas Mavericks), Leandro Barbosa (who was with the Indiana Pacers last year), and Courtney Lee (who was playing last season with the Houston Rockets). Avery Bradley has been hurt most of the year. And, of course, they’re still trying to fit in Jeff Green, after he missed the entire season with heart surgery. While the Lakers have been a spectacularly bad team this season, the Celtics are doing pretty bad as well as not many expected this team to be under .500.

Rondo leads the league in assists with 11.1 dimes per game. He’s also averaging 13.7 points per game (tying a career-best) as well as a career-high 5.6 rebounds. As always, we’ll keep you updated with Rajon Rondo’s condition.

UPDATE: ESPN has confirmed that Rondo has a torn ACL and will miss the remainder of the season.