Howard suffered a Grade 1 sprain of the ligament in his left knee during the first quarter of Tuesday's 110-106 loss. He finished with seven points and 13 rebounds in 26 minutes.
Howard wasn't a full participant in Thursday's shootaround, but after the session he was doing one-on-one drills with assistant coach Josh Powell while wearing a heavy knee brace.
"I felt pretty good out there," Howard said after the session. "The most important thing is that I'm at least 90 percent to play. I don't want this to be something that bothers me for the rest of the series. I'd rather get rid of most of the pain as possible so I can give my teammates 100 percent."
If Howard can't play,Clint Capela starts at center.
Team medical officials told Howard he normally would need seven to 10 days to recover from the sprained knee.
Howard suffered the injury in the first quarter on Tuesday. He left the game in an attempt to loosen up the leg and returned, but coach Kevin McHale took him out in the fourth quarter.
Howard expressed after Wednesday's practice there was still some pain and felt like he couldn't play that night if the pain hadn't subsided.
Howard was asked if he could play Game 2 if the knee didn't improve in time.
"I'd have to sit," he said Wednesday. "I've got to listen to my body. The most important thing is that I'm healthy. Nobody can understand an injury when they're injured but the person that's injured. This is going to be on how I feel. If I feel like I can tolerate it and go out there and play through it, then I will. But my career is the most important thing, and I want to do whatever I can to help this team, but I can't help the team if I'm hurt."
With the Rockets trailing the best-of-seven series1-0, the odds of them advancing to the NBA Finals is greatly reduced without him and places more pressure on leading scorer James Harden to produce.
In the history of the NBA playoffs, teams leading 1-0 in a best-of-seven series win the series 77 percent of the time. If said teams take a 2-0 lead, 94 percent of those teams win the series. There have been 16 teams to rally from these deficits. The Rockets franchise has done it twice (1994 and 1995) and the team went on to win the NBA title.
This Rockets team rallied from a 3-1 series deficit to beat the Los Angeles Clippers in the conference semifinals.
Howard's health was an issue during the regular season, when he missed a total of 41 games, including nearly two and half months of the regular season with swelling in his right knee.
Howard returned toward the end of the regular season. After playing on a minutes restriction, he has been a force in the postseason.
He is averaging 16.4 points and a playoff-leading 13.8 rebounds per game.