Luciano Spalletti was left scratching his head at VAR after it intervened to rule out Jhon Lucumi's late goal in Juventus' 2-2 draw with Rennes in the Europa League.
Zeki Celik had given Juventus a fifth-minute lead at the Allianz Stadium on Thursday before Mousa Al Tamari's clever flick beat Guglielmo Vicario soon after to level things up.
Rennes took the lead just before half-time through Boulaye Dia's penalty, but the hosts hit back with a spot-kick of their own, with Nick Woltemade converting from 12 yards out.
And with the spoils looking set to be shared, Juventus thought they had snatched all three points when Lucumi saw his shot deflect off Abdelhamid Ait Boudlal and into the net.
However, the goal was ruled out after a VAR review, with Lucumi deemed to have been in an offside position when Teun Koopmeiners flicked on Douglas Luiz's free-kick.
"I didn't understand it, and I'm going to look into it," Spalletti said of the incident. "When I saw it in the dressing room, I was surprised and disappointed.
"The Rennes player could have cleared that ball and Lucumi didn't impede him. I thought I knew this rule, but after the game I have a lot of doubts.
"The referee was very good, but a little less good on this incident."
The result saw Juventus drop points for the first time in the Europa League this season, though they still sit seventh in the 36-team standings heading into MD4.
Spalletti elected to start Woltemade and Randal Kolo Muani for the first time this season, with the on-loan Newcastle United striker impressing.
Woltemade also teed up Celik for the Bianconeri's opening goal, while his strike saw him become only the third player to have scored in each of his first three appearances with Juventus in the major European competitions, after Darko Kovacevic in 1999 and Roberto Baggio in 1990.
Kolo Muani, meanwhile, had a less impactful display. He only fired off one shot while having just 24 touches, the fewest of any starting outfield Juventus player.
The Frenchman was replaced in the 80th minute by Jeremie Boga, and Spalletti said he expected more from Kolo Muani and Woltemade despite the latter's performance.
"They did well, but I think I can expect more from both of them, because their qualities are greater than the performance they gave," Spalletti added.
"What the two of them produce isn't just the sum of their individual qualities. They can coexist, and when they work together, they can become three, not two."