London: Manager Arsene Wenger faces one of the toughest challenges of his 15-year reign after Arsenal crashed to their worst ever defeat in European competition on Wednesday and now face an uphill task of salvaging some tangible success this season.

Their 4-0 thumping at AC Milan in their Champions League last 16 first leg was their heaviest loss since they first played in Europe in 1963 and British newspapers on Thursday were merciless in their condemnation of their performance.

Wenger - who is usually fiercely loyal to his players no matter how poorly they may have played - was uncharacteristically brutal, saying the display was "a disaster".

"It was a shocking result and a shocking performance. It was of those nights you ever forget. It is our worst night in Europe. We were punished and deservedly so," said Wenger.

"We were never in the game, we were very poor offensively and defensively. There was not one moment in the 90 minutes we were really in the game, and it was always the same problem, balls over the top and we were well beaten.

"It is difficult to analyse, so it is better not to talk too much, to analyse with a cooler header and regroup for the next game."

Arsenal travel to Sunderland for an FA Cup fifth round tie on Saturday, a week after winning 2-1 there in the Premier League to move fourth.

But last week's match-winner Thierry Henry will not be around to revive their fortunes again after his loan spell ended on Thursday with his return to New York Red Bulls.

Wenger added: "The season is not finished. We have a big game on Saturday and it is a good opportunity to show we have character and mental strength, that we can respond after such a shocking defeat."

"DONE FOUR" Newspaper headlines told their own story with the Daily Mirror proclaiming "No Way Back for Worst Ever Gunners", The Times saying: "Henry Denied Last Hurrah As Woeful Arsenal Are Mauled in Milan" and The Star declaring: "Wenger Is Done Four".

Arsenal's abject night began on a painful note when Kevin-Prince Boateng, who used to play for Arsenal's rivals Tottenham Hotspur, blasted in a superb opening goal after 15 minutes.

The misery continued with two goals from Robinho and a penalty from the outstanding Zlatan Ibrahimovic on 79 minutes.

Milan still had two or three attempts after that and were able to rip Arsenal to shreds almost at will.

To add salt to their wounds, the defeat came exactly a year to the day since Spurs beat AC Milan 1-0 at the San Siro at the same stage of last season's competition. Their already depleted defence was also hit by a knee injury to Laurent Koscielny.

So what went so wrong for a skilful team who nevertheless has often shown resilience, guts and a never-say-die attitude under Wenger over the last decade and a half?

The defence was woeful with one mistake after another including an unfortunate slip by Thomas Vermaelen which allowed Robinho the time and space to score Milan's third soon after halftime and effectively kill off the game and the tie.

Former Ireland striker Tony Cascarino wrote in The Times: "I'm amazed that Arsene Wenger is blind to the inability of his Arsenal team to defend.

"There's always someone who steps up to the plate to make a mistake. Whether its Laurent Koscielny not tracking defenders, Bacary Sagna stopping as opponents rush forward, Thomas Vermaelen slipping over or Johan Djourou getting turned, as happened last night for the four goals scored by AC Milan."

Others pundits said Wenger was wrong to leave the improving and impressive teenage winger Alex Oxlade-Chamberlain on the bench until the 66th minute and not to have started with Henry.

Whatever the reasons, Milan totally outclassed Arsenal, now a shadow of the side that reached the Champions League final in 2006 with the club now risking at a seventh straight season without a major honour.