Andy Murray through to Mexico Open quarter-finals

Andy Murray won through to the quarter finals in Acapulco. Picture: Getty

Murray, seeded second, struggled with his first serve throughout but won 72 per cent of points on his second serve to keep himself in the box seat.

He converted only three of the nine break-point opportunities he mustered, but that proved enough to see off the Portuguese number one in straight sets and secured the Scot a last-eight encounter with Frenchman Gilles Simon.

Murray struggled mightily in the early stages of his first-round match against Pablo Andujar and it was a similar story here as he found himself an immediate break down at the start of the first set.

The 26-year-old wasted two points for an instant break back, but got on the board in his next service game and then earned two more break points, finally converting at the fourth attempt with a flat cross-court forehand for 2-2.

Murray appeared to have broken again for 4-2, but, in a bizarre incident which saw the Scot challenge when he thought his shot had been called out - in fact it had not - he appeared to be punished for verbal interference and the point was given to Sousa, who went on to level at 3-3.

That seemed to spur Murray on, though, as he broke at the next opportunity and served out to take the set.

And that trend continued at the start of the second as a slew of errors from the Portuguese gave Murray the early breakthrough.

The set progressed on serve but Sousa was hanging in there on his own delivery, facing deuce or break points in every game before Murray served out in game 10, capitalising on his second match-point.