Collins, 33, has been an important player for the Rams since he joined the club last summer on a two-year deal.
This season he has been potent in front of goal as he has contributed to 13 goals directly in 25 all-competition appearances.
And Barker believes that scoring goals is an art and Collins has mastered that art by scoring at multiple clubs in different spells.
He stressed that Collins cannot be questioned if he is doing his job in scoring, after the Rams forward scored a brace against Fleetwood Town on Wednesday night in the EFL Trophy.
“Scoring a goal is an art and James Collins has done it throughout his career”, Barker said on RamsTV about Collins.
“The only time we should question him, when he is not scoring, and he has not done that over a regular basis since he has been at Derby.
“He has been pretty consistent.
“We probably expected a little bit too much from him at the start and we are starting to see why he is so valuable and why he is so important.
“Not only to a squad but a starting eleven.”
Collins will be looking to remain a big goal threat for Derby for the rest of the season as the Rams chase promotion to the Championship.