The England camp have fingers crossed he will be fit in time for Saturday's Test, but Bath No.10 Olly Barkley training with the squad on standby.
Grayson has stepped into the No.10 role vacated by shoulder injury victim Jonny Wilkinson, and clocked up his four hundredth Test point during England's defeat against Ireland.
He is the top points-scorer in this season's Championship with forty-three, which included a twenty point haul when England defeated Calcutta Cup rivals Scotland last month.
If Grayson does not recover in time for the Wales game, then Woodward could turn to either Barkley or his Bath colleague, sixty-one times capped Mike Catt.
Catt's season has been hampered by injury, but he is hugely-experienced in the Test arena and was a key member of England's Rugby World Cup squad.
He made a telling contribution to the Rugby World Cup campaign by taking tactical control of England's quarter-final against Wales in Brisbane after appearing as a half-time substitute.