The 30-year-old - who made 11 GUINNESS PRO12 appearances last season - is likely to start the quarter-final against Argentina this weekend with Munster flanker O'Mahony now ruled out of the rest of the tournament with knee ligament damage.
Paul O'Connell's World Cup is also over after suffering a torn hamstring while the men in green are also sweating on the fitness of fly-half Jonathan Sexton who left the field against France with a groin injury.
Yet Best believes the likes of Henry are more than capable of stepping up to the plate in the knockout stages.
"You don't like to lose players, but the reason that you build a squad, the reason that you blood people in the summer or in previous internationals is for this," said Best. "We aren't stupid - we know that we are not going to go through a tournament without an injury.
"Against France, Johnny Sexton goes off early and Ian Madigan comes on and has a cracking game. Paul O'Connell goes off and Iain Henderson comes on and does well. Chris Henry was brilliant in that last quarter.
"The victory was sweet - it was real testament to the character shown after a reasonably poor performance last week to turn it around for this weekend."
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