The Arsenal manager, Joe Montemurro, expressed his frustration at conceding two goals as Arsenal had to come from behind at Rush Green to beat West Ham 4-2.

“It’s frustrating that we copped two goals,” said Montemurro. “They were set pieces, goal-kicks, and we’ve not had a problem with those all season but for some reason we got our shape wrong. It’s crazy but that’s football.”

Two goals from Daniëlle van de Donk and a debut goal from Janni Arnth helped Arsenal make up for their defensive fragility to gain a second testing victory against the Hammers.

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And the manager was pleased with the performance of the Danish defender Arnth, who was handed her first start: “It was evident that she is an experienced defender. She controlled her area, her passing was fantastic, her final pass was fantastic and that’s what we want.”

Arnth has been brought in along with Katrine Veje from Montpellier to help shore up a heavily depleted squad. “It’s well-noted the number of players we’ve got in rehab and coming back,” Montemurro said. “I think they were all sitting in the grandstand. There were seven of them. That’s a million-dollar bench there. It’s crazy. They’re all slowly coming back.”

The injury-hit Gunners’ unbeaten run collapsed against their title rivals Manchester City at the start of December – their last league outing – and they needed a bright start. With Kim Little back in the starting XI 84 days after sustaining a broken tibia, and Arnth also on the pitch, the Arsenal lineup looked a little more robust after the winter break.

A cautious opening 10 minutes was eventually enlivened by a West Ham goal. With Alisha Lehmann and Brianna Visalli putting in impressive shifts out wide in a front three, Lehmann’s curling cross found the former Manchester City forward Jane Ross at the far post and she swept in to put the Hammers ahead.

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West Ham’s manager, Matt Beard, is also struggling with a lengthy injury list. “This game was probably a week too soon for us with the injuries that we’ve got unfortunately; we had only one fit sub on the bench today,” he said. “That highlights the issues we have. We had to adjust a few things. Yesterday Julia Simic broke down which was a big blow for us because she’s been pulling the strings in midfield and we missed that a bit today, that little bit of composure, keeping the ball and linking up.”

But with two signings coming in this week who will be available to face Manchester City next weekend, and having tested the league leaders, it is not all doom and gloom.

“I think we’re looking at the champions in Arsenal. Both games this season we’ve given them a run for their money. We can take a lot of heart from the performance today.”

Beth Mead’s corner was powered into the top-right of Becky Spencer’s goal off the head of her fellow England international Leah Williamson to give Arsenal their equaliser and the Gunners then cranked up the pressure. A Spencer double-save from Vivianne Miedema after some nice work by Mead on the left kept the sides level but moments later Arnth headed home from another Mead corner to give the visitors the lead.

Facebook Twitter Pinterest Janni Arnth wheels away after giving Arsenal a 2-1 lead. Photograph: TGSPhoto/Rex/Shutterstock

As half-time approached, Arsenal were punished for their profligacy. A goal-kick from Spencer was flicked on by Visalli to Ross who, catching Katie McCabe out of position, sprinted clear and swept the ball past Pauline Peyraud-Magnin.

Undeterred, Arsenal continued to raise the tempo after the break. In the 59th minute they regained the lead as a McCabe ball across goal found Van de Donk, who poked home at the back post.

She then took her WSL tally to 10 for the season. A cleared Mead corner was returned to the forward by Little and a second cross was headed home by Van de Donk.

Next Sunday West Ham play title chasing Manchester City while Arsenal host Chelsea, who they put five past unanswered at Kingsmeadow. Will it be as easy? “Of course not,” said Montemurro. “They’re in a good state, they’re growing. We’re still about two or three weeks from having a full squad. It’s going to be a crucial match for us. We’re playing at home which is really important for us but lets be honest, Chelsea are champions of England and a very very good team.”

City lose ground in title race

Manchester City fell two points behind leaders Arsenal, who have played a game less, as they were pegged back by Bristol City. Nikita Parris’s 11th league goal of the season was cancelled out by Lucy Graham’s second-half penalty after Jen Beattie caught her in the area.

Beth England scored in the sixth minute before Chelsea ran out 3-0 victors over Everton. Drew Spence and Hannah Blundell’s second-half goals secured victory. Chelsea remain third, five points off Arsenal.

Birmingham kept pace with Chelsea after Meagan Sargeant headed in Lucy Staniforth’s free-kick in the 89th minute at home to Reading. Kerys Harrop had opened the scoring but Remi Allen levelled things one minute before Sargeant’s winner. Ini Umotong scored as Brighton defeated Liverpool 2-0 – their second win of the season.