Blackett's own goal helps Arsenal thwart Manchester United

Manchester - Tyler Blackett's late own goal compromised Manchester United's hopes of automatic Champions League qualification as Arsenal drew 1-1 at Old Trafford in the Premier League on Sunday.

The hosts took the lead when Ashley Young crossed for Ander Herrera to volley home, but Arsene Wenger's side earned a point in the 82nd minute when Theo Walcott's shot nicked off Blackett and looped over United substitute goalkeeper Victor Valdes.

The result kept Arsenal two points above United in third place in the table and the FA Cup finalists can secure a Champions League group-stage berth by winning at home to Sunderland in their game in hand on Wednesday.

Liverpool's 3-1 loss to Crystal Palace on Saturday meant that United were already guaranteed at least a place in the Champions League play-off round, which was the minimum requirement when Louis van Gaal took up his post as manager last year.

But of more pressing concern is the future of goalkeeper David De Gea, heavily linked with Real Madrid and who may have already made his final United appearance after being forced off by injury in the second half.

Arsenal were unchanged for the sixth game running - the first time that has happened since January 1994 - and as has been their approach in recent major showdowns, they were content to let their opponents attack them.

It led to a number of half-chances for United, with Young, Radamel Falcao, Chris Smalling - captain in Wayne Rooney's absence - and Juan Mata all threatening.

A slip at the other end by Phil Jones gave Arsenal a sight of goal, but despite being flat on his front, the United centre-back improvised brilliantly by swiping the ball away from Olivier Giroud with his head.

It was United, though, who were making the running, and they took the lead on the half hour.

Young stood up a cross from the left flank and with two defenders drawn to the giant Marouane Fellaini, Herrera met the ball flush on the volley at the back post to claim his eighth goal of the season.

Exit Falcao

Arsenal failed to muster a single shot on target in the first half and when Giroud's knock-down fell kindly for Alexis Sanchez early in the second, the Chilean shanked a shot high into the East Stand.

The game was a last chance for Falcao to impress the United fans after a frustrating loan spell from Monaco, but he spent much of the first half on his backside, the victim of a slippery pitch, and gave way for former Arsenal striker Robin van Persie on the hour.

The apologetic wave Falcao gave as he left the pitch suggested he will not be seen at Old Trafford again in a United shirt.

Giroud, Van Persie's successor as Arsenal's attacking figurehead, belatedly got in behind the United defence moments later, but after neatly beating Marcos Rojo to Mesut Ozil's cross, he was thwarted by De Gea.

"David de Gea, we want you to stay!" chorused the Stretford End, betraying their fear that the Spain international is destined for Madrid.

When Arsenal did find a way past De Gea, Aaron Ramsey lobbing a shot over him from Sanchez's pass, Rojo was on hand to hook clear.

De Gea had to depart the fray moments later after an awkward landing, enabling the shaven-headed former Barcelona goalkeeper Valdes to come on for his United debut, four months after joining the club.

Valdes had not played a first-team game for over a year and his first task was to pick the ball out of the net after Walcott's shot nicked off fellow substitute Blackett and looped over him.

Both sides had chances to win it, but Giroud could only shoot into the side-netting and Van Persie then ballooned over from Fellaini's knock-down.