The fifth seed overcame Frenchman Benoit Paire 4-6, 6-4, 7-6(3), saving three match points en route to his two-hour, four-minute victory at the ATP 250 tournament.
The Serbian, who is a two-time quarter-finalist in Buenos Aires, saved three match points at 4-5, 0/40 on Paire’s serve as he demonstrated his battling qualities in a hard-fought encounter. Lajovic rallied from a break down three times in the decider, before finding his top level in the tie-break to triumph.
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The 31-year-old now leads Paire 3-2 in their ATP Head2Head series, with this his second victory over the World No. 50 on clay (Sao Paulo 2016). Lajovic will play either clay-court specialist Pablo Cuevas or Argentine Federico Coria in the second round. The 36-year-old Cuevas is a six-time tour-level champion, with all of his titles coming on clay.
Paire, who was making his third appearance in Buenos Aires, was looking to build on his Australian Open third-round run this week in Argentina.