The Frenchman moved to the Reebok Stadium on transfer deadline day in August and took a while to settle into Owen Coyle's team, but has been given a run in the starting line-up over the last month.
He has only scored twice so far, although both have been in rare victories for his struggling team, and Reina has spent enough time training with the 22-year-old to know he can give Wanderers a cutting edge.
"He is a great player," the Spain international said. "I remember saying to him he was not going to Bolton until after we'd played them in the first half of the season and that's what happened.
"He has been important for them, scoring a few goals, and he will be a threat, but they have plenty of other threats."
Reina added on the club's website: "They are physically very strong and can always give you a game at home. It will be tough but we know every game will be difficult.
"They create chances, especially from corners and free-kicks, it's always difficult. They are under pressure, there is a lot at stake and it's a must-win for both clubs."
Manager Kenny Dalglish sold Ngog for £4million as the striker never looked like being able to hold down a regular first team place having scored just 19 goals in 94 games.
"He has nothing to prove to anyone other than possibly himself," said the Scot when asked whether he thought the Frenchman would be additionally motivated.
Second-bottom Bolton have not won at home in the league since November 6 but the Reds boss is wary of taking that fact too lightly.
"They've had a tough time at home. Last season they were a bit more productive there - so we just hope that run continues," he added.
"It's not going to be easy for us. They're fighting for their lives at the bottom of the league and we've got ambitions to try and move up the league, so it's going to be a difficult game.
"They've lost Gary Cahill (to Chelsea) but they have been resilient under Owen Coyle in previous years.
"This year is probably the worst position they've been in since he came in.
"I'm sure they'll be working hard to resolve that and we don't want a backlash from them."
