Best is to spend the 2014/15 campaign at the iPro Stadium after agreeing a season-long stay from Blackburn Rovers.
The 27-year-old has already made two competitive outings for his new employers, in league and cup competition.
He is yet to get off the mark, but McClaren is confident that a player who has endured his fair share of injury troubles in recent years can get back to his best as part of an ambitious Sky Bet Championship side.
He said in the Derby Telegraph: "Leon has not developed his full talent, although he has had injuries.
"He seemed to find his home at Newcastle United, where he scored goals and looked a good player.
"We want Derby to be his second home where he feels comfortable and starts fulfilling his potential again.
"He is capable of doing that. He is only 27 and we believe in him."
While backing Best to make a positive contribution, McClaren admits that the former Coventry City man has been brought in to provide cover for last season’s 25-goal top marksman Chris Martin.
He added: "Leon is somebody we have always been looking for to challenge Chris, to be behind him and sometimes play with him.
"We know if we get injuries we can put Leon in and he can score goals for us.
"He came on at Carlisle and looked dangerous. He took a knock, a dead leg, when he challenged the goalkeeper but he ran it off and contributed in the end."