Lappin, 27, told BBC Radio Norfolk: "It was a big plus having him back.
"People might think he's a physical presence, which he is, but he has more than that. He's a leader on the park and a good talker."
Lappin benefitted from fellow midfielder Andrew Crofts' Wales call-up to grab his first start of the season against the Gills.
Boss Paul Lambert has added to his options in the middle of the park this summer and Lappin, who made 50 appearances in the last campaign, is up to the challenge of vying for a starting berth.
"It can only benefit the squad," added Lappin. "It keeps everyone on their toes and it's good for the team.
"As long as we all stick together and do what we've been doing there's a belief we'll all do OK, but we've got a tough one [at Scunthorpe] on Saturday now."
Source: BBC Sport
Source: BBC Sport