Marsh (4) and Pooran (11) have been the standout stars for LSG in the IPL so far this season but Markram has been quietly going about his business and rose to the occassion when the pair were dismissed early by Rajasthan.
He went on to score 66 off 45 balls and anchored the entire innings as LSG set an imposing total of 180/5 in their 20 overs.
The Royals made an admirable chase but ultimately fell two runs short as the Super Giants won the match and Markram was named man of the match.
"From a mental space, he [Markram] would have come into the IPL not in the biggest contract. You're playing with Marsh and Pooran, you probably felt that he'd be the guy to take the backward step there," Boucher told ESPNcricinfo's TimeOut.
"I think when Marsh left for personal reasons, that's when Markram sort of came into his own because he almost adopted that 'I'm the senior player here' [position]. And with Marsh and Pooran getting out [early in this game], I thought that brought the best out of him as well.
"Aiden is a natural leader and he is leading South Africa for those reasons as well. So when an opportunity like that arises, he'll take it on himself to say, 'Right, I'm the guy who they trust now to bat through the innings and if there's a risk to be taken and a smart risk at that, I'm the guy who'll have to do that'.
So it almost forces his hand, which I think sometimes brings the best out of player, certainly brings the best out of Markram."