Defending champion Rafael Nadal was below his best as he beat Juan Monaco in the second round of the Argentina Open.
In a rematch of last year's final, top seed Nadal defeated Monaco 6-4 6-4 to reach the quarter-finals in Buenos Aires on Thursday.
Nadal was playing for the first time since suffering a shock first-round loss at the Australian Open last month, and it showed as he was broken twice and made 15 unforced errors in the first set alone.
It was also Monaco's first tournament in six months after overcoming a wrist injury, but Nadal managed to do enough to advance to the last eight.
Standing in the way of Nadal and a semi-final berth is Italian Paolo Lorenzi.
Lorenzi rallied to beat Diego Schwartzman 4-6 6-3 6-1 at the ATP 250 tournament.
David Ferrer - the second seed - barely raised a sweat in his straight-sets win over local Renzo Olivo.
Ferrer needed just 72 minutes to see off the wildcard 6-2 6-2.
The three-time Argentina Open champion will play fellow seed Pablo Cuevas in the quarters.
Uruguayan eight seed Cuevas accounted for Santiago Giraldo 6-4 6-2.