With ongoing speculation surrounding his future, reports suggested Ronaldo asked not to be picked.
But Juve director Pavel Nedved denied the rumours, insisting it was a “shared decision” not to start the five-time Ballon d’Or winner.
“He is absolutely staying at Juventus,” Nedved told broadcaster DAZN.
Ronaldo, 36, replaced Alvaro Morata on 60 minutes and thought he had headed in an injury-time winner from Federico Chiesa’s cross, only for the goal to be ruled out by VAR for offside.
Returning boss Allegri chose Morata to lead the line in a front three that also included Paulo Dybala and Juan Cuadrado, who were both on target.
Dybala opened the scoring inside three minutes, before Cuadrado doubled the lead with a low drive.
After the match returning coach Massimiliano Allegri played down the controversy, saying that he was always planning to bring on Ronaldo.
“Cristiano is OK… It’s the start of the season and seeing the condition everyone is in and thinking about the game, especially at the beginning, I put him on the bench knowing that there would be a need for him to come on,” he told broadcaster DAZN.
“He made himself available, like everyone. He played well, even scored a goal but unfortunately it didn’t stand.”
Allegri’s Juve looked to be cruising to victory when Paulo Dybala, wearing the captain’s armband, and Juan Cuadrado put them two ahead midway through the first half.
But two second-half blunders from Juve ‘keeper Wojciech Szczesny allowed Udinese to take a point through Roberto Pereyra’s penalty and a Gerard Deulofeu strike.