Greek teenager Stefanos Tsitispas continued to impress when he advanced to the Estoril Open quarter-finals by knocking out top seed Kevin Anderson 6-7 (3-7) 6-3 6-3.
Tsitspas used a more aggressive approach after the lost first set to claim victory in a two-hour slugfest with South Africa's world No.8 in Portugal.
The 19-year-old continued his impressive progress after breaking into the world's top 50 by reaching the Barcelona Open final which he lost to Rafael Nadal on Sunday.
Weather conditions in Estoril saw high gusts of wind sweep through the Millenium centre court but Tsitispas said this did not affect his mentality to win.
"It was hard to deal with the wind today but I adjusted to the conditions," he said.
"Sometimes, luck is involved and sometimes advantage is with the server but luckily, I adjusted and beat the conditions to win."
Spain's Pablo Carreno-Busta faired better than Anderson in his match against Argentina's Nicolas Kicker, sailing through to the quarters 6-1 7-5.
Tsitispas is to open Friday's play against Spain's Roberto Carballes Baena, the world No. 77 who battled back from a set down to edge Britain's Cameron Norrie 5-7 6-2 7-6 (7-1).
Carreno-Busta will be last on the Millenium court to play the winner of Chile's Nicolas Jarry and fellow countryman Ricardo Ojeda Lara.