VAR makes controversial Champions League debut

Since the start of the knockout stages, referees have been able to use VAR in the Champions League for the first time.

The addition of the technology has brought its fair share of controversy with it, with various incidents subject to intervention.

Roberto Rosetti, head of referees at UEFA, has described the use of VAR during the last-16 first legs as "perfect", but doubts over how it is used are appearing.

First use during Roma vs Porto

The first real sighting of VAR came at the Stadio Olimpico when it was used four times during Roma's win over Porto.

The first signs were positive as Adrian's goal was given after video referees checked it for a possible offside.

VAR also overruled the referee's decision to give a penalty to Roma after handball from Pepe.

The explanations of Ajax's disallowed goal

One of the major pluses of UEFA's instalment of VAR is that decisions can be explained on social media after a game has finished.

That's exactly what happened when Nicolas Tagliafico's opener for Ajax was eventually ruled out for offside, with UEFA demonstrating how the officials concluded that Dusan Tadic was interfering with play from an offside position on Twitter.

"For me its not offside," said Ajax boss Erik Ten Hag afterwards.

"I'm a great defender of VAR," said Sergio Ramos. "There are times when it's been bad for us and in this game it's ruled out an important goal."

VAR 'against' Atletico Madrid

Despite their impressive 2-0 win over Juventus at the Estadio Wanda Metropolitano, Atletico Madrid were not happy with the decisions made by VAR.

Referee Felix Zwayer overturned his decision to award Diego Costa a penalty after replays had shown the foul had come outside the penalty area.

Alvaro Morata was then denied his first goal for the Rojiblancos when his header was disallowed on review after he was adjudged to have fouled Giorgio Chiellini beforehand.

"If they think a 1.87 metre guy can fall that like, let them think that," said Diego Simeone.

No monitors in Germany

Perhaps the most farcical incident came under Spaniard Carlos Del Cerro Grande's watch at the Veltins Arena.

Del Cerro Grande had no access to pitch-side screens during Schalke's match with Manchester City and had to rely on the officials sitting in the mobile VAR room outside the stadium.

The referee gave two penalties against Manchester City, taking several minutes to give each decision because of the lack of pitch-side monitors.

Nicolas Otamendi, who gave away the first penalty by blocking a shot with his arm, was also sent off for the visitors.

"I'm a big fan of VAR," said Pep Guardiola afterwards. "The penalty is a penalty. The second one is as well. The offside [is correct] too. And the red card could be a red card.

"VAR would've changed things last year against Liverpool [in the Champions League quarter-finals]."