HOUSTON – The Boston Celtics were focused on slowing stars James Harden and Jeremy Lin when they faced the Houston Rockets on Friday night.

That left reserve Greg Smith free to make some big plays.

Harden scored 21 points and Smith added 20 to help the Rockets to a 101-89 win over the Celtics.

“They were going to overcompensate,” Houston Coach Kevin McHale said of Boston’s defense on Harden and Lin. “So if you roll behind there is going to be some openings, and Greg did a great job of presenting himself, catching and finishing around the basket.”

Smith hit eight of nine shots, grabbed six rebounds and had three blocks.

“I was in the right spots at the right time,” Smith said. “I knew if they passed the ball to me, the best thing I could do is finish it.”

Harden had 10 points, four assists, two rebounds and a steal in the third quarter as Houston built its lead.

The Rockets used a 9-2 run capped by a 3-pointer by Harden to open the period and go on top 52-47. They never trailed after that and cruised to the victory.

“In the third quarter we didn’t stop them,” Boston’s Kevin Garnett said. “We were trying to create some defensive consistency and we just weren’t able to do that.”

Paul Pierce led Boston with 18 points after scoring a season-high 34 in the Celtics’ double-overtime win at Dallas on Wednesday.

The Celtics haven’t had a great start to the season, but thought they had turned a corner recently after winning two in a row.

“We took a step back tonight,” Pierce said. “We were playing every other quarter. We’ve got to come out with the right mindset to be consistent.”

Harden, who had scored 30 or more in his last two games, got off to a slow start before heating up in the third quarter. Chandler Parsons added 15 points and Omer Asik had nine points and 10 rebounds for the Rockets, who won their second straight.

Rajon Rondo had 15 points, 13 assists and four steals for Boston, but also committed seven turnovers. Garnett chipped in 14 points for the Celtics, who shot 40 percent.

“We had some runs, but I never felt like we were going to win the game tonight,” Boston Coach Doc Rivers said. “I don’t know why and I’m disappointed in the loss.”

Rondo tried to swipe the ball from Harden as he dribbled near the 3-point line with less than 5 minutes remaining. But he missed the ball and fell to his hands and knees as Harden pulled up and swished a 3 to extend Houston’s lead to 91-83.

Another nifty play came about 11/2 minutes later when Parsons stole a pass by Rondo. Parsons dribbled down into the lane before kicking it out to Toney Douglas for a 3-pointer. Douglas added a three-point play a few seconds later after a missed 3-pointer by Pierce to put Houston up 99-85.

The Celtics had cut the lead to five with a 6-2 run before Carlos Delfino hit a 3 for Houston with about 8 minutes left.