When Arsenal click as they did for 12 whirlwind minutes at the beginning of the second half, it can feel as if all of their problems, the well-documented angst and the soul-searching, are nothing more than tricks of the imagination.

In a game that they had to win, after the dispiriting Premier League losses to Manchester City and Chelsea, they started badly and left themselves needing to scramble up an incline, if not a mountain, after an early concession to Jack Collison.

Yet Lukas Podolski pegged West Ham back before his team showed style and ruthlessness immediately after the break to pull to within four points of fourth place and script happier headlines. The composition of Arsenal's half-time brew might need to be tested. This was an awesome demonstration of their attacking potential and West Ham had no answers.

The visitors' bleak evening was compounded when the substitute Danny Potts was carried off wearing a neck brace after almost 10 minutes of treatment, having lost consciousness in a sickening aerial collision with Bacary Sagna. The West Ham manager, Sam Allardyce, reported that Potts had "hit the ground like a dead weight" with the "double blow" being the manner in which he landed on his head.

Potts was detained in hospital overnight and Allardyce hoped the problem would be nothing more serious than concussion, which will keep the defender out of action for at least two weeks. Allardyce had sent on the Arsenal target Mohamed Diamé as his final substitute and so his team had to play the final seven minutes plus 12 minutes of injury time with 10 men.

The pick of Arsenal's goals was Santi Cazorla's bewitching flick but the rugged power of Podolski's equaliser ran him close. Olivier Giroud, twice, and Theo Walcott also showed a clinical edge. West Ham's bright opening had floated away on the icy breeze and the business of picking up the pieces now begins. They have taken five points from an available 24.

Arsène Wenger had talked beforehand of being "a bit backs to the wall," of his worry at the lack of consistency and yet the unpredictability here was glorious. "Was I worried at 1-0 down? I thought it was an interesting test," Wenger said. "But we kept going, even though I could not have predicted we would have scored five. What was vital was that we equalised before half-time."

Podolski's hat-trick of assists proved key to the second-half thrills but it was his equaliser that was the turning point. His team's early offensive work had been disjointed and the jangling nerves were almost audible when Collison lashed a sweet drive past Wojciech Szczesny.

But Podolski pulled Arsenal out of a familiar pickle when he took Jack Wilshere's pass and clubbed a vicious drive from 25 yards into the far corner. Wenger described the Germany forward's display as his "most efficient" for the club. "He took the responsibility at the moment that we needed him to," Wenger said.

West Ham had presented a physical challenge and it was possible to detect nerves at the outset in the Arsenal backline when the visitors launched high balls. Collison's first goal of an injury-truncated season came after Giroud's headed clearance from Matt Taylor's corner fell to him on the edge of the area. His touch and blast rocked Arsenal. It was only West Ham's sixth away goal of the season. There was emotion in Collison's celebration with the club's head physiotherapist Andy Rolls.

Allardyce felt West Ham had been comfortable at the end of a first half marked by loose defending. Podolski had a shot smuggled off the line by Joey O'Brien while at the other end, Aaron Ramsey raced back to clear Carlton Cole's goalbound dink past Szczesny from in front of the line. Thomas Vermaelen suffered minor ankle damage as he attempted to intervene. Walcott threatened and Cazorla had a free-kick well saved by Jussi Jaaskelainen.

But Arsenal blazed out of the blocks in the second half to reduce West Ham to rubble. Allardyce lamented a soft concession from Walcott's corner, when Per Mertesacker's screening of James Tomkins allowed Giroud to dart in and profit, but Cazorla's magical finish from Podolski's pass took the breath. Podolski then crossed for Walcott and Giroud.

"It was a horrible 12 minutes for us," Allardyce said. "When they hit top gear, we just couldn't live with them. They tore us apart."