"There may well be a few surprises," said Dallaglio, who featured in each of the last three Lions tours and was a series winner in South Africa 12 years ago.
""There might also be a couple of players who we have yet to see play international rugby who might get a chance. Just because you are not playing international rugby doesn't mean the Lions selectors will ignore you, as was the case with Will Greenwood in '97.
"What people have to understand is that the Lions is not just about picking the best players, it is about picking the best tourists, it's about picking people who have the right characteristics. This is not a holiday they are going on."
Dallaglio points to four Englishmen in particular who may be seen as outsiders but who could yet make the plane to South Africa.
Among Dallaglio's tips for possible inclusion are his former Wasps colleagues Josh Lewsey and Danny Cipriani, two players both he and McGeechan know extremely well.
"It is about what style of rugby they want to play on the hard grounds in South Africa," Dallaglio told the Daily Telegraph.
"There is no doubt that guys like Josh Lewsey merit consideration, but there are also many other players in similar situations.
"Danny [Cipriani] fits into a category with a number of players - Jonny Wilkinson and Ben Foden. You can't take them all but there might be one or two who fulfil the criteria.
"Danny hasn't had as much game time in the bigger games as he would have liked but sometimes when it is a close call between one player and another, you go for the devil you know rather than the devil you don't."