Arsenal are the only unbeaten side left in the competition. Arteta's men topped the 36-team league phase with a perfect eight wins from eight, and across the entire campaign have lost just two of their last 22 Champions League matches (W17 D3). Their quarter-final, however, was a study in defensive suffering — winning 1-0 in Lisbon through Havertz's late goal, then holding out for a goalless draw at the Emirates against a Sporting side that pushed them hard.

Domestically, Arsenal ended a damaging four-game losing streak by winning 1-0 against Newcastle on Saturday, restoring their three-point lead at the top of the Premier League. Bukayo Saka returned in that game — his impact is irreplaceable: Arsenal average 2.6 goals and 2.3 xG per game when Saka plays in the Champions League this season, compared to 1.5 goals and 1.8 xG without him.

Atlético's route here was altogether more cinematic. Simeone's men won 2-0 in the first leg against Barcelona at the Metropolitano, before enduring a 2-0 deficit in the second leg — only for Ademola Lookman's strike to settle the tie 3-2 on aggregate. Atlético have also posted their highest-ever goal tally in a Champions League campaign — 34 goals, eclipsing their previous record of 26 from the 2013-14 run to the final. Most recently, they beat Athletic Bilbao 3-2 at the Metropolitano on Saturday — Sørloth bagging two goals and Griezmann scoring the other — ending a four-game La Liga losing run.

Atlético have never lost a Champions League knockout-stage game against an English team at home. Their record reads P6 W3 D3, against Chelsea, Leicester, Liverpool, Manchester United, Manchester City and Tottenham — none of them Arsenal. Tonight is the first time these clubs have met in the Champions League knockout rounds. The last time they faced each other in European competition, Atlético eliminated Arsenal from the 2017-18 Europa League semi-finals, winning 2-1 on aggregate.

Arsenal hammered Atlético 4-0 at the Emirates in the league phase back in October — whether that result carries relevance four rounds later is the central tactical question. Simeone will have dissected it obsessively. Tonight is also Antoine Griezmann's final home Champions League appearance before joining MLS outfit Orlando City — a decade of service, played out in his last European night at the Metropolitano against a club with its own unanswered European longing. Team news: Atlético are without Barrios (hamstring) and Giménez (muscle). Lookman and Hancko are both doubts. Arsenal have Saka back — their most important attacking player in this competition. Gyökeres has failed to score in four knockout matches while attempting just six shots; 28 players have attempted more since the round of 16 began.