Burgess has signed for English Premiership side Bath and will move from Australian NRL team South Sydney Rabbitohs in October in a bid to make England's World Cup squad next year.
But with the 2015 tournament in England starting in September, Lancaster said there was not much time for him to learn the game.
"It's great news for rugby union," Lancaster told Sky Sports on Monday.
"He's a world-class rugby league player and credit to Bath for having the courage to sign him. He's got a massive learning curve ahead of him - time is short for the World Cup but he's a special player so we'll see how he goes."
Lancaster expects the 25-year-old league forward to challenge for a place in England's midfield if he can get up to speed with the nuances of union.
"It's going to be tough - to arrive in November and learn the game, play the game and also earn the right to play on merit ahead of the players we've got," said Lancaster.
"It's a competitive position and while he's a good player, there's a lot of intricacies to learn.
"In my experience it is easier to make that transition as a back. There are less of the complexities of the forward play to learn - scrums and line-outs and everything that goes with it."
Burgess has represented his country in rugby league 13 times, scoring seven tries, and Lancaster hopes he can follow the blueprint of Sonny Bill Williams, who began his career in league before switching to union to help New Zealand win the 2011 World Cup.
"I think he's got the ball skills and pace to play in the back line - and the physicality - and if you put him alongside some of the other players we've got, he'd be exciting. You have to give him every chance," Lancaster said.
"Sonny Bill Williams is probably the best example of making the transition. He was a forward in league and a back in union and he made the transition gradually.
"It's going to be fast-track for Sam but if there's one player who you'd think has a good chance of doing it, it would probably be him."