Mathews' return was a prior arrangement based on "personal grounds", a Sri Lanka Cricket release said, though he had also suffered a hamstring strain during his match-winning 54 not out on Sunday. Pradeep, meanwhile, injured his hand in the opening T20, and Gunathilaka has been laid low by a back complaint. It is unclear how long Mathews will be unavailable, but Pradeep and Gunathilaka are ruled out of the tour. Vice captain Dinesh Chandimal will lead the side in Mathews' stead.
The triple blow is a significant for Sri Lanka's chances in the limited-overs series' - all three players have featured in Sri Lanka's ODI sides, and Mathews especially, provides balance to the XI in his all-round role.
The three-wicket win on Sunday was Sri Lanka's first victory of the tour. The third T20 international is scheduled for January 25, and five ODIs are to follow.
The injuries to Gunathilaka and Pradeep may also affect availability for the forthcoming T20 tour of Australia.