Injury and international duty has limited the midfielder to just five appearances in 2013 but he has played 23 times since his £2million switch from Feyenoord last summer.
Lambert told the Express & Star: "There's still more to come from him. He's only really been here seven or eight months or so.
"It's his first season in the Premier League, but he's definitely a good technical footballer, that's for sure.
"Against United I thought he came on and was excellent. He's been unlucky.
"He's had a hard time with injuries. He had an ankle problem and then obviously he was away with Morocco at the Africa Cup of Nations, which we couldn't do anything about.
"Then he returned and hurt his knee against Everton in his first game back."