The 26-year-old forward - who has three senior England caps to his name - saw his season start slowly thanks to injury, but has made more appearances in recent weeks and scored the only goal against Sunderland last week.
His form has come as a timely boost to Lambert's side, with Darren Bent struggling and Benteke still adapting to Premier League life.
|GABBY TO GRAB ANOTHER?|
|3/1||Gabby Agbonlahor is 3/1 to score against Manchester United at any time with bet365|
"He's really quick and when he gets up to speed, he is a handful. If he can get goals to go with his game, he will be really fine."
Lambert says he is pleased with Agbonlahor's link-up play with Benteke, believing the two attackers can help his young side grind out results in their next three fixtures against both Manchester sides and Arsenal.
"Gabby and Christian look a threat," continued Lambert. "The two of them are a handful at the moment for anybody.
"[As a team] we've been on a bit of run. When you get a bit of a run or achieve a good result, everyone comes in for the week feeling buoyant. This week has been no different.
"To beat someone like United you need a bit of luck. We also have to believe that we can win. The belief in the football team at the minute is there. We are going to have to play well against them that's for sure."