Sir Graham Henry says a Lions series victory would be an "astronomical" achievement which can further propel Warren Gatland into the All Black coaching frame.
Henry, the only man to have coached the All Blacks and British and Irish Lions, told the BBC: "He's one of the most experienced coaches in the world, he's had a long run with Wales and won a couple of Six Nations.
"He's been with the Lions for some time and done exceptionally well. The All Blacks are currently the world champions and ranked number one in the world.
"So to beat the All Blacks at home with a side which has had very little rugby together would be an astronomical achievement. Warren's done a great job in getting them all together and he's possibly a future All Blacks coach."
Henry initially described the Lions tour schedule as a suicide mission, a view accepted by many pundits. So while he brought a powerful side to New Zealand, Gatland has already beaten the odds by levelling the series in Wellington.
All Blacks coach Steve Hansen is expected to call it a day after the next World Cup, with his assistant Ian Foster seen as the establishment favourite to take over. But overseas-based coaches led by Welsh boss Gatland and Ireland's Joe Schmidt cannot be discounted.
Gatland coached the Lions to a 2-1 series victory over a weak Australian side four years ago, and was and was the forwards coach for the 2009 tour to South Africa, assisting Ian McGeechan.
The Lions lost that series 2-1, although they lost the second test at the death and then crushed the home side in the final game.