DHAKA - South Africa's T20 captain Faf du Plessis and pace spearhead Dale Steyn are in doubt for the team's opening World T20 match against Sri Lanka on Saturday. The pair both have hamstring injuries which kept them out of South Africa's final warm-up match against Pakistan on Wednesday. A final call on their availability will be taken on Saturday afternoon, shortly before the match.Steyn mildly aggravated the right hamstring strain he suffered during the third Test against Australia in South Africa's first practice match against Bangladesh A yesterday. Steyn bowled 2.2 overs before leaving the field and has since been receiving treatment. This follows a 10-day recovery period after Steyn initially sustained the injury on the first day of the Test. Then, he bowled 10.1 overs before being unable to continue and took no further part in the first innings effort. Steyn bowled three overs in the second innings but was left out of the T20 series against Australia to complete his rehabilitation program.In a press release CSA said Steyn "will continue to receive treatment from the physiotherapist to give him the best chance of recovery for the opening match." When the South African squad left for Bangladesh last Saturday, their team manager Mohammed Moosajee was hopeful Steyn would be ready for the warm-up match and even more optimistic he would play the first match.They are less confident of du Plessis appearing in their first game. The captain did not play in the Bangladesh A game at all and is a "50-50 chance" for the Sri Lanka match. "The medical team is cautious of rushing him too soon because of the explosive nature of T20 cricket and the back-to-back schedule of fixtures," CSA's release read. "He will continue to receive extensive treatment and rehab to give him the best chance of regaining full fitness for the opening match."If du Plessis is ruled out, AB de Villiers will likely lead and bat at No.3, in his absence. De Villiers was in charge of the T20 squad from June 2011 to December 2012 when he stepped down because he felt overburdened by the treble role of captaining, keeping wicket and batting in the top order. He remains South Africa's ODI skipper but has been relieved of the gloves in the limited-overs formats. South Africa's other injury worry was Morne Morkel, who hurt his right shoulder during the Tests against Australia. Morkel did not play in any of the T20s against Australia but appears to have recovered fully. He bowled his full quota of overs in the match against Bangladesh A and played in the warm-up match against Pakistan.With Morkel fit and four other seamers, Lonwabo Tsotsobe, Wayne Parnell, Albie Morkel and Beuran Hendricks in their ranks, South Africa are unlikely to call for a replacement to Steyn just yet. Should they need one, Kyle Abbott is the obvious candidate. He was in the squad for the T20s against Australia and was the second highest wicket-taker in the domestic 20-over competition with 16 scalps, behind Hendricks.