Sanchez wizardry can't hide Wenger's ongoing problems
Middlesbrough 1 Arsenal 2
It is victories like these that mean Arsene Wenger will probably keep his job as Arsenal manager, but while he may continue to sit on the Emirates throne, it is unlikely he will ever do so comfortably again.
This was an important win for the Gunners, their first win on the road since January, but in the wider scheme things, it had a largely pointless feel.
Arsenal's pursuit of a top-four finish looks a little flimsy, their chances of remaining a Champions League club slight at best. They are seven points behind Manchester City in fourth, albeit with a game in hand, yet this victory over a Middlesbrough team who have not won a league game since before Christmas will not silence any of Wenger's critics for long.
The rebellion has begun and if Wenger stays, he will have defied rather than quelled it.
Boro are a club who give the impression relegation would not be a disaster. Under Steve Agnew, given a short-term contract following the departure of Aitor Karanka last month, they have slipped quietly into the drop zone and appear to be heading back to the Championship with a shrug.
In other words, Arsenal should win games like this, so when they make hard work of doing so, nobody is impressed.
No matter what happens in the summer, whether Wenger stays for another year or two, or decides it is time to stand down, it will never be quite the same again. Things have changed, opinions have altered, opposition has hardened. There is too much animosity that has become entrenched.
The tide has shifted and Wenger will find he is constantly swimming against it. He has been criticised before, but it has never been as widespread as this. He has provoked anger at times, but never with this level of sustained ferocity. There have been doubts but he has always managed to answer them with the top-four finish to keep Arsenal's major shareholders happy.
Managers do not necessarily lose their jobs when so many fans want them to go, but they rarely manage truly to redeem themselves when things get as bad as this. Never before under Wenger have Arsenal reached this stage of the season looking less likely to secure a Champions League place.
Rarely have they looked so vulnerable and Boro, in desperate need of a win, sensed it. They were on the front foot, threatening to breach Arsenal's new-look three-man defence, as Grant Leadbitter went close with a long-range strike.
Marten de Roon had the ball in the back of the net before half-time, but Arsenal's backline had stepped out, catching the Dutchman offside as he headed Gaston Ramirez's cross.
Arsenal looked like a team that had lost four away games in a row and although Aaron Ramsey had a shot cleared off the line by Antonio Barragan, they were well contained by their hosts until a moment of brilliance from Alexis Sanchez.
When Adam Clayton clattered into Granit Xhaka on the edge of the area, it was the ideal position for the Chilean to keep goalkeeper Brad Guzan guessing as to which side he would put the free-kick and the American duly stood, studs glued to the turf, as the ball was curled into the top corner to his right.
Given Boro had failed to score in six out of their last eight games, Arsenal should have had few worries, but the hosts were level four minutes into the second half. Sanchez lost the ball to De Roon, who passed it on to Stewart Downing. He advanced down the right flank, cut inside, looked up and delivered a cross over the head of Laurent Koscielny, which was stabbed in by Alvaro Negredo.
An all too familiar defensive lapse from an Arsenal perspective. Wenger's switch to a back-three for the first time since 1997 did not make them noticeably less vulnerable.
"I felt it added a bit more stability on the long balls," explained Wenger. "We faced a direct game and we have been punished a bit on that. It gave the opponents more of the ball. Against Palace we had 70pc possession but lost.
"Sometimes we want to have the ball but when a team lacks confidence just to change the system can help believe something different."
The goal, only Boro's 23rd in the league this season, lit a fuse and they should have taken the lead moments later when Downing benefited from a sliced clearance from Gabriel, but failed to keep his shot down.
Arsenal were briefly in disarray and Petr Cech made an excellent save to keep out Daniel Ayala's close-range header.
For the first time in weeks, Boro looked threatening rather than ponderous going forward.
Agnew's side needed the win, though. The Ayala miss felt costly and it was as Sanchez chipped a pass to Ramsey, who teed up Mesut Ozil to restore Arsenal's lead.
Ben Gibson had a good chance to snatch an equaliser late on, but the centre-back, who will surely leave his hometown club if they do go down, could not take it.
"We responded well. It was not perfect but the commitment and focus was there," said Wenger. "At 1-1 we found a response and managed to win.
"It (the top four) is mathematically still alive. We knew we needed to win.(© Daily Telegraph, London)