Lansbury sat out the match after picking up his 10th yellow card of the campaign last week, and after watching his side record a goalless draw against the League One side, Davies insisted that Lansbury's absence from the fixture was "key".
The 49-year-old is quoted by The Express as saying: "We lacked flair and creativity and guile, and probably got what we deserved.
"I have no doubt that Henri Lansbury was key. He is a massive loss to us. This is a player who is performing very well."
The former Arsenal man has scored seven times in 26 appearances for Forest this season.