Joe Schmidt has expressed his concerns over Jonny Sexton's playing schedule after his return following a series of concussions.
The Ireland fly-half hasn't played any rugby since last November observing a 12-week rest period as he tried to recover from the head injuries.
He was given the all-clear to return to action this week, and goes straight back into the Irish starting lineup for Saturday's game with France.
The following week is a rest weekend in the Six Nations, with the Top 14 getting back underway as Sexton's club, Racing-Métro, take on Clermont.
Both sides are chasing a place in the top two, and Schmidt expects Sexton to be selected.
It would only be Sexton's fifth apperance in the league for Racing this season, with a broken jaw and the concussion problem having kept him out for large chunks of the season.
"With Racing going away to Clermont next week, I'm sure they'll want to put their best team out," said Schmidt.
"They're right up the top competing for spots, both those teams, and that would be seen as a big Top 14 game for them.
"So that's far from ideal but it's not a circumstance we can control: we control this week.
"So yes, it's a concern looking down the line, but we're very much focused on this week, if we can get a result, and if we can stay in the hunt.
"All this was a concern last year through the Six Nations as well," added Schmidt.
"I think that congestion of games (would be an issue) whether he'd had time off or not.
"But having the time off is probably the best preparation for putting together six games back to back."