Malan limped off in the 15th over after pulling up as he chased a ball to the boundary. He was padded up to bat as England collapsed in the latter part of their chase, but he continued to slip down the order and was eventually not needed.
England have four days before their semi-final, which is likely to be against India, offering them one more day than the teams who will meet at the SCG on Wednesday. However, at this stage, it seems unlikely that Malan will be able to recover in time.
If Malan is ruled out of the tournament, it will be a tight turnaround to call someone up from outside of the squad given the travel time to Australia, although England's ODI players who are part of the series against Australia that follows the World Cup are due to arrive during the week. James Vince, Jason Roy and Sam Billings are in that squad.
England have previously had to make one change to their squad with Tymal Mills replacing Reece Topley who injured his ankle stepping on a boundary marker before the warm-up game against Pakistan in Brisbane. They have so far named the same XI throughout the tournament.
Should England have to rejig their batting order for the semi-final, the role of Ben Stokes could become more significant. He effectively took Malan's spot at No. 3 in the chase against Sri Lanka and had perhaps his best T20I innings for England, guiding them home in a tense finish, although the required rate was rarely above a run-a-ball.
The semi-final will be England's first game in Adelaide for the tournament, so it will bring with it the need to adjust to its dimensions, which are longer straight and shorter square of the wicket. India, their likely opponents barring upsets on Sunday, faced Bangladesh there during the group stage.