Atletico Madrid and Arsenal played to a 1-1 draw in their Champions League semi-final first leg match on Wednesday, with both goals coming from penalties and Arsenal having a second one nullified upon review.
Sweden forward Viktor Gyökeres gave Arsenal a 44th minute lead and Julián Alvarez also converted from the spot to level in the 56th.
Arsenal thought they had won a second penalty with some 10 minutes left when David Hancko, who had already caused the first, caught the foot of Eberechi Eze.
Replays revealed there was slight contact but Dutch referee Danny Makkelie reversed his original decision after a long look at the pitchside monitor.
A potential winner for the Gunners would have also not reflected the flow of the game which Atletico completely dominated after the break following a balanced first half.
Club icon Antoine Griezmann, playing his last European home game for Atletico before as summer move to Major League Soccer, hit the crossbar, and Arsenal also had to thank goalkeeper David Raya that their unbeaten run in the competition continued.
They now have the home advantage on Tuesday at Emirates Stadium where they trounced Atletico 4-0 in the league phase in autumn.
"It was very emotional. I will always have this in my heart," Griezmann told streaming portal DAZN about his final match at the Metropolitano.
Looking at next week, he added: "It will be an interesting return leg. We wanted to win here but faced a strong opponent. But we will give our all next week to reach the final."
Gyökeres told TNT Sport: "In the first half we controlled the game quite well. And then in the second half, they started much better, maybe deserved to get a goal eventually. Overall, a tough game. We know it's a tough place to come, but it's only half-time.
"We know when we play at home, with our fans, it's going to be different, for sure. We just have to do our job, be at our best, and it's going to be a good game at home."
Neither Atletico nor Arsenal have lifted Europe's most important trophy yet, with Atletico losing three finals and Arsenal one.
The winner will face either title holder Paris Saint-Germain or six-time champions Bayern Munich in the May 30 final in Budapest.
PSG won the first leg at home 5-4 on Tuesday in a match for the ages, with the return leg in Munich next week Wednesday.
Wednesday's game was never expected to match the attacking flair provided in Paris as it featured two more defensive-minded teams.
Arsenal had a first chance, with Piero Hincapie off target with a volley at the far post after Gyökeres failed to connect with Noni Madueke's cross.
Alvarez forced a full-strech save from Raya with a drive from the edge of the area as the hosts also made their presence felt.
At the other end, Madueke's curling shot flew just inches wide but diving Jan Oblak would have probably got his gloves onto the ball.
The Gunners were ahead just before half-time when Gyökeres was pushed down by Hancko and stepped up himself to convert the spot kick into the bottom left corner, with Oblak diving the right way but the penalty simply too powerful.
Atletico came out of the dressing room a changed team as they went in search of a quick equalizer.