Alejandro Tabilo defeated Joao Fonseca 6–3, 3–6, 7–5 in the second round of the ATP 250 Buenos Aires tournament on clay on 11 February 2026, producing an upset against the pre-match favourite. Fonseca entered as the odds-on favourite at 1.57, but Tabilo, priced at 2.33, proved the superior competitor across the three sets. After taking the opener with relative comfort, Tabilo faltered in the second as Fonseca levelled the match, setting up a decisive third set. The Chilean recovered his rhythm when it mattered most, edging a close final set 7–5 to advance. The victory represents a significant scalp for Tabilo on the South American swing and demonstrates his clay-court credentials against a rising opponent.