"Players like Riqui have something special, but it is going to be very complicated for him here as there is a lot of competition. I have told him that he has a future here, and we will think about what is the best way to succeed at Barca," he added.
The visitors caught a bright start to the second half though as Robin Quaison's perfectly timed through ball allowed Jean-Philippe Mateta to halve the deficit against the run of the game in the 48th minute.
Raul Jimenez put the away side in front with a half-volley from Castelo Podence's left-wing cross, before Romain Saiss's header from Neto's corner completed the scoring.
However, Slovan failed to defend the fragile lead and the home team managed to tie things up in the final minute of overtime, forcing a penalty shootout.
The two sides went into the game with a point separating them; with Al-Nassr in second place with four points needing a win to keep them at arm's length from third-placed Sepahan.
The 33-year-old Serb now faces a semifinal against Casper Ruud of Norway, who beat fourth seed Matteo Berrettini of Italy 4-6, 6-3, 7-6 (5).
Only counting on talent and youthful nonchalance doesn't take you to the top the 59-year-old predicted.
"These two tournaments came too close to each other for me this time," she added.
The goalkeeper protected his side from a bigger defeat after neutralizing the chances from Angelino and substitute Christopher Nkunku in the closing stages.
The decision to declare Gor Mahia the 2019-20 champions in March with nine games of the season left due to the outbreak of the pandemic was upheld by a local tribunal on Tuesday.
Former Juventus and Toronto FC forward Sebastian Giovinco broke the deadlock deep into first-half injury-time with a beautifully curled free-kick from just outside the area.