Brian O'Driscoll has claimed that England centre Sam Burgess is 'not quite up to speed at international level'.
Burgess has been tipped to go to the Rugby World Cup less than a year after swapping rugby league for rugby union.
The 26-year-old won his first cap for England last weekend during their 19-14 triumph over France at Twickenham Stadium.
However, O'Driscoll believes that Burgess's performance in that game suggests that the Bath man's place in the squad is far from secure.
"His tackle technique and strength in the hit were never in question and for me, he has just the right amount of thug in him to make having a go just a fleeting thought," the former Ireland captain wrote on his official website.
"When his team has the ball though, I just don't think he's quite up to speed at international level just yet.
"I said it last season watching him play for Bath that the difference between attack play in rugby league and union is that in union the hard work starts when the player is tackled and the ruck forms. In league, the tackle completes the play with no rucking needed. Two very different mindsets."
England play the second of three Rugby World Cup warm-up matches on Saturday when they face France in Paris.
