Eastmond will make his first England start against Argentina on Saturday when he takes over at inside centre from Billy Twelvetrees, who has been called up by the British and Irish Lions.
Lancaster, the England head coach, said: "He is the first real rugby league half back who has come through and got this opportunity. He has got a strong sense of self belief in his own ability which shines through on the training field and he is a dominant player on the field, which he needs to be a decision maker and a key organiser."
He added: "You need to have an effective communication and he has got that. He made the change from rugby league to rugby union to play international rugby union and club rugby at the highest level so he is excited by the opportunity and he will have a strong sense of self belief."
Henry Paul never established himself at the highest level and Andy Farrell made the switch too late to be as effective in Test rugby union as he was in league.
In a strange coincidence, Northampton fly-half Stephen Myler, another former rugby league player, could make his England debut off the bench on Saturday.
Lancaster is confident England will not miss a beat in attack without Twelvetrees, despite the fact he had to drop out of the side at relatively late notice.
"It is as close to a straight swap as there can be," Lancaster said.
"Obviously they are different physically - Billy is tall and a bit heavier but Kyle can definitely carry and he can distribute and pass pretty much like Billy can. The dynamics of how we will try to play the game will remain the same. It is as close a swap as we could have made."
Eastmond is joined in the England back division by London Irish wing Marland Yarde, who will make his Test debut in place of David Strettle. It will be the youngest England back division since the defeat to Wales at Wembley in 1999, when Barrie-Jon Mather and Steve Hanley made their Test debuts.