Ferdinand insists Lammens, Bryan Mbeumo and Matthijs de Ligt are the three players who have been behind the team's impressive form over October and November.
Ferdinand said on Rio Ferdinand Presents: "I don't think it's one man. It can't be down to one man. (Matthijs) De Ligt has been our best defender this season, he is even adding goals for us, like the last-minute goal the other day.
"But in terms of his his press, he's assertive and has willingness to go into foreign areas of the pitch to defend at right times. His clearing out of his box is brilliant.
"(Bryan) Mbeumo has been a joke as well. He's really stepped in and been a mainstay and is someone who can give us two or three seconds on the ball, score important goals for us, create chances.
"I saw Thomas Frank's comments about him yesterday, being a complete winger. I think, by the end of the season, he will be one of the most complete wingers in the league. He can do everything, he just needs to keep consistently doing that in a red shirt."
Ferdinand added, "And the goalkeeper. You can't talk about anyone being our most important player without the goalkeeper.
"It is no coincidence with our upturn in form that we have a goalkeeper it seems all our players trust."