Mertesacker hails resolute defence as Arsenal progress
Arsenal 2-0 Borussia Dortmund
Per Mertesacker praised Arsenal's defensive solidity after a 2-0 win over Borussia Dortmund took them through to the Champions League knockout stages.
Alexis Sanchez's second-half strike settled the Gunners' nerves and the defence were able to close the game out.
They had led since Yaya Sanogo's goal just over a minute in and Mertesacker said: "That was good but we had to play another 89 minutes - and over 95 minutes we played absolutely solid and that was key.
"It was a solid performance, especially defensively. We didn't give them too much, especially in the second half, we played absolutely solid at the back."
Manager Arsene Wenger agreed with his player's assessment, particularly in light of Saturday's disappointing defeat to rivals Manchester United.
"(We had) the focus to defend well together," he said.
"We had a similar game to Saturday but we focused really well not to give any chances away."
Mertesacker added: "We've had a few disappointing results so this was a mental test, but we are strong enough and now we can continue.
"After Anderlecht and after Manchester United we dropped mentally a bit but we learnt from those disappointments and we are delighted with the performance.
"Now Saturday, an early kick-off away (at West Brom), we have to prove (ourselves) because last season we dropped a lot of points. We are through to the knockout stages and now we have to focus on the Premier League."
Sanchez has won rave reviews since his summer arrival from Barcelona.
Asked what the Chilean brought to the team, Wenger said: "Unbelievable fighting spirit and his class as well, he's a mixture of talent and desire."
The one sour note was the loss of both Sanogo and Mikel Arteta to injuries, with the latter of particular concern as Wenger battles a growing casualty list.
"It doesn't look good, it's a calf," the Frenchman said.
"It's difficult to take on the chin at moment, you go in to many games and need everyone available."
With Danny Welbeck out injured and fit-again Olivier Giroud not registered for the Champions League squad, Wenger had opted for Sanogo ahead of German international Lukas Podolski, who once again had to make do with a place on the substitutes' bench.
Wenger's faith was rewarded as Sanogo took just 73 seconds to fire the Gunners ahead, when he stabbed his shot under goalkeeper Roman Weidenfeller.
The France Under-21 forward, who has suffered a string of injury problems since signing from Auxerre in 2013, spurned a chance to add a second when he sprinted clear, only to be crowded out as the Dortmund defenders covered back.
Dortmund, who had won all four European ties despite poor Bundesliga form, slowly got a foothold in the match, but for once this season Arsenal's defence looked solid enough as the damp mist descended on north London.
In the 38th minute, Emiliano Martinez - the third-choice goalkeeper in for injured Wojciech Szczesny, who picked up a hip injury when conceding the opening goal during the 2-1 Barclays Premier League defeat by Manchester United - produced a smart reaction save with his feet to deny Henrikh Mkhitaryan.
At the start of the second half, Weidenfeller denied Sanchez with a low stop down to his left.
Alex Oxlade-Chamberlain was then unfortunate to see his sublime 25-yard volley drop back off the crossbar.
Weidenfeller was, though, beaten again when Sanchez curled in a brilliant second goal on 57 minutes, cutting inside from the left to offer his side some much welcome breathing space in their bid for qualification.
Oxlade-Chamberlain, so impressive for England during the friendly win over Scotland in Glasgow, continued to stretch the Dortmund defence, drilling an angled shot just over after cutting in from the right.
Sanogo's injury jinx struck again when he hobbled off with a hamstring problem, replaced for the final 12 minutes by Podolski, who got a rousing reception from both sets of fans.
Martinez preserved a clean sheet when he saved with his feet at point-blank range from Ramos in stoppage time.