Marta Kostyuk defeated Mirra Andreeva 7–6, 6–3 in the Brisbane WTA 250 quarter-final on hard court on 9 January 2026, producing an upset against the pre-match favourite. Andreeva entered the match as odds-on favourite at 1.78, yet Kostyuk proved the superior player across two sets, taking a competitive opening set to a tiebreak before dominating the second. The Ukrainian's performance suggests improving form at the start of the season, while Andreeva's defeat halts her momentum in Brisbane. The result will have implications for both players' ranking trajectories heading into the remainder of the Australian summer.