By ADAM TROXTELL

A surprising first leg leaves Arsenal on the brink of elimination when the Gunners head to Monaco to finalize their UEFA Champions League round of 16 encounter.

The Gunners must overcome a 3-1 deficit (3:45 p.m., Fox Sports 1) to the principality, and they have to score three goals in order to have a chance of progressing. Monaco can move on to the quarterfinal round for the first time since 2004 if it holds the advantage.

The French league side will have some reinforcements to accomplish this feat, including midfielder Jeremy Toulalan, who has returned from injury. Form is also on Monaco’s side, as the team has won four of the last five games and held Paris Saint-Germain to a draw.

Arsenal is fresh from a 3-0 win against London-rivals West Ham on Saturday and has won all four of its games since falling to Monaco in February. While Jack Wilshere and Alex Oxlade-Chamberlain will be out with injuries, central defender Gabriel Paulista has returned from his time out and joined the team in Monaco.

The Gunners at least have something on their side for this encounter. They have progressed all five times against French league opposition in the Champions League knockout stages.

Bayer Leverkusen takes a narrow 1-0 advantage into the Vicente Calderon for its second leg encounter against Atletico Madrid (3:45 ET, Fox Sports 2).

Atletico will need to put recent goal-scoring struggles behind them, with a Koke goal against Valencia remaining the only one the team has scored in the last four games. Three draws followed its loss to Leverkusen in the first leg.

Tiago Mendes will be suspended for this game after he was sent off in the first leg. Diego Godin is also suspended for yellow card accumulation.

The German club enters the contest in a better position. Leverkusen has put together five straight wins in all competitions and devastated Stuttgart 4-0 over the weekend.