Alex Iwobi bagged 90 minutes of action as Liverpool did a double over Arsenal on Saturday with a 3-1 win at Anfield following a 4-2 away win at Anfield last year.Goals from Roberto Firmino and Sadio Mane left Arsenal two goals adrift against Liverpool after 45 minutes. Arsenal improved their performance after the break but could only manage a consolation through Danny Welbeck as Wijnaldum restored the two goal lead in added time.The defeat means Arsenal slip into fifth spot while Liverpool go fourth, level on points with third place Manchester City who play Sunderland away from the Etihad on Sunday.Arsene Wenger made eight changes from the side that won at Sutton in the FA Cup and sprung a surprise by leaving Alexis on the bench. Mesut Ozil was absent with an illness.Olivier Giroud’s inclusion made plenty of sense against a side that has struggled to defend set-pieces, and you couldn’t argue with the Frenchman’s form against Liverpool, sadly his lads couldn't play to the Frenchman's strength.Giroud had five goals in his last seven Premier League appearances against Liverpool, including three in his last two at Anfield.Ragnar Klavan returned as Liverpool made one change. the centre-back replaced Lucas Leiva in defence in the only alteration to the line-up deployed against Leicester City on Monday. Dejan Lovren was back in the matchday squad after injury and was named on the substitutes’ bench.First HalfLiverpool started on the front foot but the visitors had most dangerous early attack when Giroud’s neat touch kicked off a break that ended with Oxlade-Chamberlain finding Hector Bellerin and the Spaniard standing a cross up to the far post, where Giroud was lurking. But Liverpool survived that, and then they thrived.Mane made their first goal, making the most of space on the right to size up a cross for Philippe Coutinho. The Brazilian missed his attempted flick but Firmino was the spare man at the back post. He took a touch to commit Petr Cech and lifted the ball into the roof of the net. Frustratingly, it gave a Liverpool side the confidence as they were bright and lively and threatening. Coutinho forced a reflex save from Cech with a fierce left-foot shot and Liverpool got the two-goal cushion they wanted just before the break.This time the move started on the left where James Milner attracted two markers and found Firmino. The former Manchester City man spotted Mane in space on the right side of the box with the Senegalese giving Petr Cech no chance with his tidy finish.Coutinho could have made it three when he got the wrong side of Shkodran Mustafi but shot straight at Cech with the visitors heading for the tunnel at half time with a two goal deficit.Second HalfArsene Wenger introduced Alexis Sanchez at the outset of the second half and the Gunners were more dangerous immediately.Simon Mignolet had already been forced to rush from his line and claw away a cross from the left before a similar delivery teed up Olivier Giroud for a trademark header which the Liverpool stopper superbly touched onto the bar.Arsenal did reduce their arrears on 57 minutes, however. Sanchez dispatched a slide-rule pass into the run of Welbeck off the left flank – despite a slight touch from Joel Matip – and the striker bounded through to dink a finish past Mignolet and the despairing goalline lunge of Klavan.With an element of tension suddenly added to the occasion, the Reds found themselves under greater pressure yet simultaneously with plenty of opportunities to counter attack.The correct final touch was eluding both sides, though, not least when Matip failed to head home from Coutinho’s perfect free-kick to the far post 15 minutes from time.Substitute Divock Origi was inches away from putting the game beyond the Gunners when he glanced James Milner’s free-kick onto the base of the post.But, after a crucial Matip block from Sanchez, Liverpool finally sealed the three points in stoppage-time as a breakaway saw Lallana play in Origi and the Belgian squared for Wijnaldum to slam a low finish into the bottom corner.