Atletico Madrid drew 0-0 at home to Porto in a cagey opening Champions League Group B game on Wednesday, the Spaniards spared defeat when VAR overturned a late goal from visiting striker Mehdi Taremi.
Taremi bundled the ball into the net in the 80th minute from the floor after a mix up between Atletico defender Renan Lodi and goalkeeper Jan Oblak, but the goal was ruled out as the Iran forward had handled the ball as he slid to the ground.
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The Uruguayan had also gone close to breaking the deadlock late in the first half with a free kick which cleared the wall but went narrowly above the bar.
"Porto were very good in the game, we lacked a bit of creativity and we had few chances, when you play against a team who wants to play on the counter its always difficult," said Oblak.
"Their [disallowed] goal came from a big error from us, luckily we have VAR and they gave the handball but we have to stay focused to avoid scares like that."
Porto coach Sergio Conceicao and Atletico's Diego Simeone shared a dressing room as players for Lazio and the two men have similar footballing visions which made for a tight affair with neither side affording the other much space.
After the match, Simeone said: "We have to keep improving. It will be a complex group, Milan were winning 2-1 at Liverpool and ended up losing, we could have won or lost, it's clear all the games will be competitive. We have to speed up our game, generate more intensity in midfield and up front, and we'll work to find it."
The visitors nearly took the lead early in the first half with a powerful cross from midfielder Otavio which went beyond Oblak's grasp and came off the post.
Simeone then made a triple change, bringing on Griezmann, who had been subbed off in a disappointing return to the team at Espanyol after re-joining the club on loan from Barcelona.
But it was another substitute in Angel Correa who almost gave the hosts the lead, the Argentine forward driving a shot across goal which Porto keeper Diogo Costa beat away.
Porto showed a little more ambition in the latter stages and were aggrieved when Taremi's goal was ruled out as the ball brushed against his arm just before it trickled across the line.
They had another opportunity to snatch the lead when a cross found Mbemba from close range but the defender failed to make proper contact with the ball.
Despite the lack of chances, Simeone was upbeat about the prospects of the future for Atleti in the UCL: "Working, the only way is working. You have to remember that Joao [Felix] since mid April hasn't had continuity with his injury, he's recovered in preseason, he's making an effort to find his best level and he will do it playing,
"Correa had to play, Luis arrived late, Griezmann has just arrived. So we have to stay calm and believe in what we're doing."