When asked Wednesday if he expects Rondo, who is a free agent this summer, to be in a Mavericks uniform next season, coach Rick Carlisle replied: "No, I don't."
Rondo played only 34 seconds in the second half of Dallas' Game 2 loss, benched by Carlisle after picking up two quick fouls, while defending James Harden, as well as a technical. The former All-Star logged just under 10 minutes of court time for the whole game.
Rondo had initially hurt his back about a week ago, a source said, but the point guard thought he could play through it. He did not inform the Mavericks' trainers of the issue until after he was called for a blocking foul on Harden, which exacerbated the injury, early in the Game 2 loss.
"He sustained a back injury basically at the 11-minute mark of the first quarter last night," Carlisle said. "He attempted to take a charge on James Harden, hit the ground and from that point going forward probably should not have played any more, but he did. He wasn't able to play his game or play as well as he can play. Today, it's not good, so he is going to seek additional opinions. That's where things are at with him."
Carlisle said that Rondo is not expected to be around the team for the rest of the series as he explores additional medical opinions.
Asked after the game if Rondo wanted to be on the floor, Carlisle told reporters in Houston: "You have to ask him that question. All I know right now is that we need everybody at their competitive best. This isn't about one guy who did or didn't play. This is about everybody pulling in the same direction for the organization. That's what it's about."
Just four minutes into the game, Rondo nonchalantly walked the ball up the floor and got whistled for an eight-second backcourt violation with the Rockets applying no pressure. He was then replaced by Barea some 40 seconds later after Jason Terry got loose on the ensuing inbounds pass for a wide-open 3, with Carlisle keeping Rondo on the bench until 5:30 remained in the second quarter.
Carlisle acknowledged that the announcement of Rondo's back injury would be met with some suspicion, given his poor performance and lack of playing time in the Game 2 loss.
"I understand that the announcement that's been made is going to have different interpretations," Carlisle said. "I am giving you our interpretation of it, and this is fact. From here, we're moving forward. We've got a series to win and we've got to win Game 3 with the guys that are available."
Injured forward Chandler Parsons, meanwhile, is out for the rest of the season and exploring surgical options for his injured right knee. The injury forced him to miss the final six games of the regular season as well as Game 2 of the Houston series. Parsons logged 37 minutes in Game 1 but was playing in obvious discomfort, managing just 10 points on 5-for-15 shooting.
If Rondo does not play again for the Mavericks, with free agency looming in July, Tuesday's scenes will mark a downbeat end to his time in Dallas after the Mavs parted with a future first-round pick and high-energy big man Brandan Wright to acquire Rondo in a Dec. 18 trade with the Boston Celtics.
Sources have maintained for weeks that Rondo is planning to sign elsewhere this summer after his longstanding struggles to function in Carlisle's system or mesh offensively with the likes of Mavs guard Monta Ellis. The Mavericks made the trade for Rondo hopeful that his defense, rebounding and history of big-game production as a Celtic could trump his limitations as a shooter, but Dallas' spacing with Rondo on the floor has been even worse than feared.
Rondo served a one-game suspension in late February for conduct detrimental to the team after a profanity-laced shouting match with Carlisle about play-calling responsibilities in a win over Toronto and a subsequent emotionally charged dispute in the locker room after the game.
ESPN.com's Tim MacMahon and Ramona Shelburne contributed to this report.