Top seed Sara Errani was the shock loser in Thursday's second-round action at the Abierto Monterrey Afirme.
The Italian crashed out of the tournament against Anett Kontaveit, losing 6-1 6-3 in a dominant performance by the Estonian.
Kontaveit served up five aces and won 60 per cent of points on her first serve, as well as 60 per cent of points on first return, as she upstaged her more-fancied Italian opponent in just under an hour.
There were no such troubles for number two seed Caroline Wozniacki, who beat Croatian world number 71 Mirjana Lucic-Baroni 6-4 6-4.
There were six breaks throughout the match, with Wozniacki taking four of those, as the Dane won 71 per cent of points on her first serve.
Wozniacki will now take on Heather Watson in the quarter-finals.
Elsewhere, fifth seed and 2015 runner-up Caroline Garcia cruised past Julia Glushko 6-1 6-2 to book her spot in the quarter-finals.
Garcia sent down seven aces and won 74 per cent of points on her first serve to ease through the second round, saving all five break points she faced in the process.
Qualifier Pauline Parmentier defeated Monica Puig 6-3 6-4, while Christina McHale retired against fellow American Nicole Gibbs when down 7-6 (7-5) 6-7 (4-7) 3-0.