"Gavin just felt his calf tightening in training," said Wales coach Warren Gatland.
"There is no point training on it and making it a major problem that would keep him out for six or eight weeks."
The Ospreys centre was absent from the recent autumn internationals because of an Achilles injury having also failed to play any part in the two-Test summer tour of South Africa.
Henson, who toured with the Lions in New Zealand in 2005, was a key part of his country's second Grand Slam success in four years last season and is expected to challenge for a Lions spot once more this summer.
His place in the Welsh side will be taken by fellow Lion Tom Shanklin who renews his club partnership with Cardiff Blues team-mate Jamie Roberts.
Shanklin's promotion sees Andrew Bishop step on to the replacements bench.