UPDATE 5:25 pm: An MRI on Tim Duncan has shown no structural damage to his knee, tweets Adrian Wojnarowski of Yahoo Sports and the NBC Sports Network. Duncan is listed officially as day-to-day.

That is a huge break for the Spurs, this looked like it could have been much worse. I’d still expect Duncan to miss a few games — the Spurs will be cautious — but this could have been much, much worse.

8:00 am: It was scary — Washington’s Martell Webster drives baseline and Tim Duncan helps smother his shot, but when Webster lands he falls and as he does he rolls up Duncan’s leg. It looked like the kind of situation you see more with NFL offensive linemen.

Duncan went to the ground and stayed there, grabbing his left knee (the one already with a brace). He was eventually carried off the floor by Stephan Jackson and DeJuan Blair. Duncan did not return.

He has been diagnosed with a sprained left knee and a sprained right ankle. He will be re-evaluated on Sunday and as of right now there is no timetable for his return. Players after the game said he would be fine, but that’s what teammates say. We’ll wait for the doctor’s word.

Duncan is averaging 17.5 points and 9.8 rebounds a game. He is having his best season in years and if he is out for any length of time the West-leading Spurs will miss him.