Heather Watson's defence of her Monterrey Open title came to an end in the quarter-finals as she was beaten 6-4 6-4 by world number one Angelique Kerber.

Watson fought hard but failed to convert any of the eight break points she created against top seed Kerber, who responded well to the pressure.

Watson looked undaunted in the early going, but unforced errors allowed Kerber to convert the only break point she got in the first set, edging 4-3 up.

Kerber carried momentum into the second set, breaking Watson straight away for a 1-0 lead.

Both of their previous meetings - also won by Kerber - had gone to three sets, but though Watson continued to create opportunities she could not get the break she needed to get back on level terms.

Instead she found herself on the defensive, and had to save three break points in the fifth game, keeping the deficit to 3-2.

That merely delayed the inevitable as Kerber proved too strong, setting up a semi-final against fourth seed Carla Suarez Navarro.