MONTERREY, Mexico - Given all she could handle by lucky loser Elena-Gabriela Ruse, defending champion Garbiñe Muguruza nonetheless closed out Tuesday night at the Abierto GNP Seguros with a victory.

The Spaniard rallied from a double-break deficit in the first set and was twice a break down in the second before sealing the match and a spot in the second round, 6-4, 7-6(4).

Muguruza won the last five games against the World No.230 to sneak away with the first set, and later saved a total of three set points in the second set before holding off a furious fight from the Romanian who looked to force a decider.

After opening up a 5-0 lead in the tiebreak, Muguruza ultimately needed three match points to seal victory, as Ruse's high-risk, high-reward tennis made the two-time major champion work until the end.

"It was a tough match for the first first round, it was very late, it's cold,. With all the conditions, I just had to fight and never lose the hope," Muguruza said after the match.

"I have five matches in total. Today was the first one, and I'm looking forward [to a title defense], one by one."

Despite over 200 spots between the two players in the WTA rankings, the 21-year-old Romanian hung with the former World No.1 for one hour and 43 minutes.

Ruse hit 23 winners to Muguruza's 25, and just one more unforced error (29 to 28), but ultimately, the Spaniard won the match's biggest points when it mattered most. 

The No.2 seed will next face Russia's Margarita Gasparyan, who surrendered just one game in defeating Mexican wildcard Victoria Rodriguez, 6-1, 6-0.

Elsewhere around the grounds on Tuesday, another former champion had success, as No.3 seed and four-time winner Anastasia Pavlyuchenko lost just three games to compatriot Anna Blinkova, 6-0, 6-3, while No.7 seed Kristina Mladenovic battled past Brazilian Beatriz Haddad Maia in over two-and-a-half hours, 6-4, 1-6, 7-6(5).