After three sometimes-rocky performances when Chandler Parsons was out with surprisingly nagging knee injury, the Rockets expect him to return tonight against the Celtics and are more certain than ever of how much they missed the variety of ways he contributes.

“He does so many things,” Rockets guard Jeremy Lin said. “He is a great playmaker. He impacts the game in such a variety of ways you can’t really describe them all. He’s not ball dominant so that helps us a lot and he’s a great defender.”

Parsons and Rockets coach Kevin McHale were cautiously optimistic that Parsons would be ready to return. McHale even pointed out that he said before that a player “should be good to go,” only to have the player go “out for two weeks.” Parsons’ injury was a good example. He played more than 44 minutes the day after he bumped knees with Terrence Jones in a practice, only to have the knee get sore and swollen while shooting several days later, keeping him out for a week.

“I just did a lot of shooting so I don’t know what’s going to happen between now and game time, but I plan on playing,” Parsons said. “It’s been so sore. It’s been irritating me. I don’t want it to be something that’s going to linger. I want to make sure this isn’t going to linger on. I’d rather miss three games here than miss something important during the end of the season.”

The Rockets have gone 2-3 in games in which Parsons has not played. Averaging 17.2 points and 3.6 assists, the Rockets’ offense has been most effective with Parsons’ on the floor compared to his teammates, averaging 109.9 points per 100 possessions (tied with Terrence Jones).

“He’ll cut,” McHale said of what Parsons can bring that the Rockets have missed. “He’ll move himself and cut from different areas, open the floor for different people. That’s the big thing we got to get better at, opening space on the floor for others by making unselfish cuts and just moving it. That seems to come and go like the weather for us.

“He knows how to play. Understanding spacing, understanding where you’re going with the ball, understanding what your teammates’ strengths and weaknesses are … makes it easier. If you’re out there living in your own little bubble of ‘how’s this affect me, how’s this affect me, how’s this affect me’ – and about half of this league plays in that bubble – it’s just hard. Space on the floor is a big thing. The more space you have the better everybody is.”