The Northampton fly-half suffered a minor strain to his left calf muscle during training on Tuesday.

The England camp say that he is expected to be fit for Saturdays Twickenham encounter, but Bath fly-half Olly Barkley is remaining with the squad.

Grayson has stepped into the number 10 role vacated by shoulder injury victim Jonny Wilkinson, and clocked up his 400th Test point during Englands defeat against Ireland 11 days ago.

He is the top points-scorer in this seasons championship with 43, which included a 20-point haul when England defeated Calcutta Cup rivals Scotland last month.

If Grayson does not recover in time for the Wales game, then England coach Sir Clive Woodward could turn to either Barkley or his Bath colleague, 61 times-capped Mike Catt.

Barkley, capped three times as a replacement, has lost his seat on the England bench this week, with Catt recalled to Englands 22 by Woodward.

Catts season has been hampered by injury, but he is hugely-experienced in the Test arena and was a key member of Englands World Cup squad.

He made a telling contribution to the World Cup campaign by taking tactical control of Englands quarter-final against Wales in Brisbane after appearing as a half-time substitute.