The Red Devils produced a convincing first-half display but were unable to break the deadlock in their Group A opener in Miami, with both sides settling for a point.
Gradišar, who came off the bench in the final 10 minutes to replace Palestinian forward Wessam Abou Ali, shared his mixed emotions after the match.
“I am disappointed we didn’t get the win,” the Slovenian wrote on Instagram.
“But at the same time, proud to have had the chance to play against my idol, Lionel Messi. It is a moment I will remember forever. Thank you to all the fans for your support.”
“We will come back stronger and give everything we have in the next match,” he added.
Ahly will face Brazilian side Palmeiras on Thursday, with both teams seeking their first win of the tournament.
Palmeiras were also held to a goalless draw, by FC Porto, in their opening game.
The-22-year-old, joined the Cairo giants in January from Hungarian side Fehérvár FC.
He has scored five goals in 19 appearances across all competitions since his arrival.
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