General manager Sam Presti said tests Sunday morning revealed that Maynor had torn the ligament in the fourth quarter of Oklahoma City's 98-95 victory at Houston on Saturday night and will need season-ending surgery.
Maynor is the primary backup to All-Star Russell Westbrook and was averaging 4.2 points and 2.4 assists in 15 minutes per game this season. Maynor finished each of his first two NBA seasons in the top 10 in the league in assist-to-turnover ratio. He had averaged more than three assists for every turnover both seasons.
"Eric's a smart player. He understands that position and understands that role because he's been with it for a while with us. He was great with that unit," coach Scott Brooks said Sunday night. "We have to figure out how we're going to move forward with it but Eric is a really, really good player and it's not easy losing him."
Maynor's injury is the first disruption to Oklahoma City's 10-man rotation, which had been intact from last season's run to the Western Conference finals. That gave the Thunder an advantage with a shortened training camp and limited practice time in an NBA season condensed by the lockout.
Now, Brooks must figure out the best way to move forward without Maynor. The Thunder have two other reserve point guards, rookie Reggie Jackson and veteran Royal Ivey, and Brooks said James Harden could also play the point instead of on the wing.
"We have options," Brooks said. "Reggie definitely will get an opportunity, we have Royal and we also can throw James there. James has obviously been a great playmaker and getting better as the games and experience that he acquires go by. But I think Reggie's going to have a great opportunity for him."
Jackson was Oklahoma City's first-round draft pick, selected 24th overall out of Boston College. He has already played in three games, mostly late in blowouts, but now could get more meaningful minutes.
"That's the thing about the NBA. You've got to be ready to play," Brooks said. "This is his opportunity to be ready and he will make the best of it."
Maynor's knee buckled as he drove the lane in the fourth quarter against the Rockets. No one made contact with him. Teammates carried him off the floor.
Perhaps Maynor's biggest moment in the spotlight since coming over in a trade from Utah during his rookie season was in Game 2 of the Western Conference finals against Dallas last year, when he played well enough that Brooks kept him on the floor throughout the fourth quarter of Oklahoma City's only win in the series.
"One of the things I know about Eric, he's a tough kid. That backup point guard spot is a very challenging spot because you don't get a lot of minutes," said Brooks, who spent his NBA career as a backup point guard.
"When things go well, you get a little credit. When things go bad, you get all the blame. I played it for a lot of years but Eric had the mental toughness to go through all that."
Presti said the Thunder are confident that Maynor "will do everything necessary to come back from this injury and be prepared for the 2012-13 season."
In the meantime, Jackson will get an audition for a bigger role.
"If you play hard and you play for your team, you're usually in a good place," Brooks said. "He doesn't have to go in there and score 20 points. He doesn't have to have 10 assists. He just has to be solid."