Mathews was adjudged timed-out as he failed to receive his first ball within 3 minutes of the dismissal or retirement of the outgoing batsman.
"After the fall of a wicket or the retirement of a batsman, the incoming batsman must, unless time has been called, be ready to receive the ball, or for the other batsman to be ready to receive the next ball within 3 minutes of the dismissal or retirement. If this requirement is not met, the incoming batter will be out, timed out," says the ICC rule for timed-out.
However, the umpires can adjudicate according to the playing conditions of the World Cup, and in this case Mathews took more than 2 minutes to receive his first ball before he was ruled timed-out.
Mathews failed to receive his first ball as he was unhappy with the straps of his helmet. Taking note of it, Bangladesh Captain Shakib Al Hasan appealed for a timed-out dismissal, and the umpire obliged.
An irritated Mathews did not leave the field immediately, and engaged himself in explaining to the umpires and Shakib the reason for him for the delay in receiving his first ball.
Television visuals showed Mathews indicating his straps of the helmet to the umpires and Shakib, but could not convince them, and took a long way back to the pavilion.