Cristiano Ronaldo was sent off on his Champions League debut for Juventus but two Miralem Pjanic penalties secured the 10 men a dramatic 2-0 win at Valencia.

Ex-Real Madrid forward Ronaldo was dismissed just 29 minutes into his much-anticipated return to Spain following an off-the-ball incident involving Jeison Murillo.

Referee Felix Brych consulted with his assistants and brandished a straight red for Ronaldo's apparent attempt to pull Murillo's hair, meaning the 33-year-old, who was reduced to tears in the aftermath to the dismissal, could miss a reunion with former club Manchester United in October, if UEFA chooses to extend his mandatory one-match ban.

While Ronaldo’s presence has raised hopes Juve can end their 22-year wait for European success, the Bianconeri demonstrated they can still prosper without him as Pjanic's spot-kicks either side of half-time secured a hard-earned three points on the road.

Mario Mandzukic, Sami Khedira and Blaise Matuidi all squandered gilt-edged chances before Ronaldo was given his marching orders, although Massimiliano Allegri’s men refused to be flustered by the incident.

Pjanic kept his cool amid the heated Mestalla atmosphere, converting his first penalty on the stroke of half-time following Daniel Parejo's wild high boot on former team-mate Joao Cancelo, who moments earlier had cracked a shot against the crossbar.

Official Brych pointed to the spot again six minutes after the interval, allowing the Bosnia and Herzegovina international to double the Serie A side's advantage after Murillo had bundled Giorgio Chiellini to the floor.

Midfielder Pjanic picked out the bottom right corner and Allegri's men held on for a winning start in Group H, though not without a late twist to an action-packed tale as Wojciech Szczesny saved a contentiously awarded Parejo penalty in stoppage time.