Robinson has been plagued by career-threatening back and knee injuries and has not played competitive rugby since withdrawing from the Bledsoe Cup match against Australia in July 2004.
The six-time capped All Black subsequently underwent surgery to shave a piece of spinal disc that was pressing on his sciatic nerve and to repair knee cartilage and looked unlikely to play again.
However Robinson, who brought a fearsome edge to the New Zealand pack as demonstrated in the wins over England last summer, made significant progress by coming through a rigorous contact session on March 23rd.
But Henry has refused to speed up the forward's return in time to face the tourists, despite having limited options at lock.
"He's only 28 so he has at least another three or four years ahead of him," he said.
"It would be silly to rush him through to play against the Lions if that was going to end his long term future in the game.
"He doesn't feature in our Lions planning. If he becomes available, that will be a bonus. He's waiting to see what the reaction is to the training session, which will be the test.
"If Chris Jack was injured we would have no senior locks playing.
In that worst case scenario, Henry could employ several promising young locks playing in the Super 12 at the moment, including the Hurricanes' Ross Kennedy, Sean Hohneck at the Chiefs, Kevin O'Neill for the Crusaders and the Highlanders' James Ryan.
The former Wales coach added: "Kennedy has made positive progress from the NPC, which is pleasing, but those guys are probably 18 months to two years away from international rugby.
"But then we might not have any choice."