Cristiano Ronaldo was sent off in his first Champions League match for Juventus, leaving the Portugal star close to tears as he walked off the pitch.

Ronaldo was dismissed in the 29th minute of Juve's 2-0 Group H-opening win at Valencia on Wednesday after tangling with defender Jeison Murillo.

After Murillo went down inside the area, the Portugal forward gestured for his opponent to get up, then put his hand on the Valencia defender's head and appeared to tug his hair. Referee Felix Brych showed Ronaldo a straight red card after discussing with his assistant behind the goal.

Ronaldo looked baffled and kept professing his innocence, sitting down on the pitch in disbelief. The five-time world player of the year was clearly distraught as he left the pitch, still shaking his head. It was his first red card in 154 Champions League games, and the decision means he could miss a return to Old Trafford when Juventus plays Manchester United next month if he gets at least a two-match ban.

According to UEFA rules, a player who is sent off is suspended for the next match in a UEFA club competition. And in case of "serious offences," a UEFA Control, Ethics and Disciplinary Body could increase the punishment and even extend it to other competitions.

Juventus host Young Boys next in the competition before two straight games against United, with the first match at Old Trafford on Oct. 23.

The 33-year-old Ronaldo joined Juventus from Real Madrid in the offseason and scored his first two goals for the Italian club this past weekend in a 2-1 win over Sassuolo in Serie A.

Ronaldo is the Champions League all-time leading scorer with 120 goals and led Madrid to the title the past three years in a row.