Former Arsenal striker Niall Quinn believes the club's Champions League hopes rest on how they deal with Schalke 04's Klass Jan Huntelaar and Ibrahim Afellay, at the Veltins Arena on Tuesday.
The pair scored both the goals as the Bundesliga side defeated The Gunners at the Emirates Stadium a fortnight ago, leaving Arsenal second and putting the club's European hopes in jeopardy.
And following a lifeless display in defeat to Manchester United in the Premier League last weekend, Quinn admits Arsenal face a tough task to get their European Cup hopes back on track against Schalke.
"I know I wasn't the only person concerned by Arsenal's performance at Old Trafford on Saturday - as has been highlighted by many onlookers, it was an abject display and as such one that was pretty alarming," Quinn told Sky Sports.
"Losing is one thing but the manner in which the players seemed simply to accept that United were the better team was disappointing and there's no doubt that they need to work on their application, starting with the trip to Schalke.
"Arsenal players have always played for the shirt and early on in the season, at Anfield and the Etihad in particular, the team's spirit looked great and the work-rate was first-rate, but you'd have to question just how good it was at the weekend.
"They can't afford a repeat showing at the Veltins Arena, where Schalke will be out to strengthen their grip on Group B."
While Arsene Wenger's side created little going forward, at the back, a defence, which is the best domestically, wilted in the face of Huntelaar and Afellay, who both caught the north Londoners unawares to propel the Germans to the top of Group B.
Arsenal can now ill-afford to lose further ground on Huub Stevens' side with another defeat, and Quinn believes stopping their nemesis' from the first group meeting between the two will be crucial in achieving a positive result.
"As Schalke proved at the Emirates when Klaas-Jan Huntelaar and Ibrahim Afellay did the damage, they are a strong, pacy and economical side," Quinn added.
"Their all-round organisation impressed me a lot; they are difficult to break down at one end but have more than enough ability to overrun you at the other unless you can match them.
"They are a very, very decent football team - the spine of their side is strong and Arsenal will have their work cut out to deal with them."