Richard Johnson has been given until Saturday morning to prove his fitness ahead of the NatWest Series final against South Africa at Lord's.

After his sparkling Test debut, in which he took six wickets against Zimbabwe at Durham, Johnson missed all three games of the NatWest Challenge against Pakistan with a knee injury. He returned in time for the start of the NatWest Series and has since taken seven wickets in six matches.

However, he had to leave the field against South Africa at Edgbaston during England's four-wicket win with groin stiffness, but Michael Vaughan is confident he will be fit for the final.

Vaughan said: "He seems all right and has had a decent bowl this morning. But with any injury you have to wait until the next day to see how he wakes up. It will be important for us because he has been an invaluable member of the team since he has come in."

"Having Richard Johnson in the side is a huge help," added Vaughan. "If he'd been fit for the Pakistan series he'd have been batting at No. 9 and we'd have probably gone in with five bowlers then as well. He's been a huge bonus for me as captain to have him coming in at No. 9 and obviously the way he's bowled in the series."

If Johnson is not passed fit, England will probably choose between the wayward Steve Harmison, or the novice Kabir Ali.