South Africa's Andre Nel is expected to replace injured fast bowler Dale Steyn for the third Test at Edgbaston.Steyn has been ruled out of the match starting on Wednesday because of a broken thumb.He sustained the injury while fielding a ball that was driven back to him off his own bowling during the second test at Headingley on Monday.Coach Mickey Arthur said he was confident that the strength in depth in the squad would allow South Africa to adequately replace Steyn.Arthur said: "Missing a player of Dale's calibre is a huge blow but I feel we have such good depth with the likes of Andre Nel and Monde (Zondeki)."Nel is probably next in the queue. That was why I was strong on wanting good reserve strength with experienced players who know about the intensity of test cricket."South Africa have a 1-0 lead in the four-match series.