Lin, who has missed the past two games with a right chest contusion, will come off the bench, a change from his normal starting role.
"I'm feeling good," Lin told the team's website after Friday's shootaround. "I get to play tonight, so I'm happy about that. I worked out yesterday, went through some stuff and felt good. The trainers were up there watching and said as long as nothing crazy happens today I'm good to go.
"It feels great [to be back]. It's been a really, really long week, so just the fact I get to play is a huge, huge burden off my shoulders."
The point guard was injured in the first half of Game 2 and didn't play after halftime. He started Game 3 but scored just two points in 18 minutes.
Lin's normal backcourt mate, James Harden, is also expected to play Friday despite being diagnosed with strep throat.
With Harden not 100 percent, Lin will help.
"Jeremy feels a lot better today," Rockets coach Kevin McHale said. "We'll bring him off the bench and see how much juice he's got in the tank. It's always hard to enter a series when you haven't played for a while but, hey, we're going to try to keep what we've got going. We'll definitely try to fit him in there and see how he is and see how his arm feels -- most importantly, if he gets hit or anything happens.
"Playoff series end up kind of having a life of their own. To be thrown in the middle of that rhythm a lot of times is really hard. ... That's why we've got to be a little bit careful. Jeremy hasn't played in a while, and not only has he not played, he hasn't been able to shoot or do anything with any kind of contact for a week or so, so that's always hard."
The eighth-seeded Rockets are trying to become the first team in NBA history to overcome a 3-0 deficit.