Goals from Alexandre Lacazette and Henrikh Mkhitaryan in the first half were enough to see off Southampton, as we kept chase with the Champions League places in a composed win.Unai Emery made some changes for the game, one was enforced, the others were for rotation purposes.Ainsley Maitland-Niles succumbed to illness and would have come back into the side, so Stephane Lichtsteiner kept his place on the right of defence.Mesut Ozil made way for Aaron Ramsey in the Number 10 spot, and Pierre-Emerick Aubameyang was left on the bench for Alexandre Lacazette. We also had Matteo Guendouzi on the bench, with Granit Xhaka and Lucas Torreira comprising the engine room.We had the perfect start to the game, going a goal up inside six minutes. Saints defenders were convinced the Frenchman was offside, but Laca knew better, and he punished them with a low drive from close range. Only a minute before, Saints should have been a goal up, but Redmond wasted his chance, and we went up the other end and Laca got his goal. Saints weren’t finished though, and twice went close within a minute. First, Kolasinac blocked a close range header, only for Matt Targett to fire a low shot that Leno did well to push away. It was clear our opponent weren’t happy with sitting back.We weren’t exactly happy with sitting back either, and on the 17th minute, we doubled our lead.Alex Iwobi’s pass was deflected into the path of a lurking Mkhitaryan, and the Armenian made no mistake, firing low and hard past Angus Gunn to give us daylight in the scoreline.We kept up our attacking, perhaps an indicator we are more comfortable with the 4-2-3-1 formation we were using - and before half time, aside from a couple of scares from young winger Yan Valery, we should have had another couple.First up was Lacazette, who saw his shot superbly stopped by Angus Gunn, and then Mkhitaryan should have put the game to bed but failed to get on the end of a cross/shot by mere centimetres.The half time whistle sounded, and Southampton were clearly relieved. We had punished them and should have put the game out of sight, but the second half would give us further opportunities to end the game as a contest.Ralph Hassenhuttl had seen enough in the first half to know that a change was needed, and Charlie Austin and Michael Obafemi came on for defender Jack Stephens and midfielder Stuart Armstrong. Austin had scored in every appearance against us in his career, and now that Saints had two frontmen, they would cause us more problems, though Mustafi and Sokratis had dealt with the Saints well in the first.It changed the complexion of the game, and Granit Xhaka gave the ball away to Ward-Prowse on the edge of the area, with the midfielder drilling just wide. It was a warning and a let off for us.This game wasn’t over.We made our first change of the game after ten or so minutes - Lichtsteiner received a knock so made way for Koscielny, with Mustafi covering on the right. We were holding firm, but another goal would have really made us comfortable. As it was, one goal would change the complexion of the game, and Saints were getting back off the canvas and looking intentful.We then created our first real chance of the second half, but no one was there to get on the end of Ramsey’s tantalising low ball into the box. It was his last action too, with Ozil coming on to replace the Welshman. With twenty minutes to go, we still had our two goal advantage and we were dealing with the threat from Saints quite comfortably. Games change in seconds, but we looked to have stolen Saints thunder early on and never let them recover.With fifteen minutes left, we brought on Aubameyang for Alex Iwobi. The Gabon man would be keen to harness those minutes to keep tabs on Aguero and Salah at the top of the Golden Boot chart.It didn’t take long for Ozil to make his presence felt, and his exquisite reverse pass found Auba. The striker attempted a pass into the box but Vestergaard cleared well. Ozil’s pass alone deserved a goal.With minutes left on the clock, Saints went close, and we had Leno to thank for denying them. Targett let fly with a twenty yarder, and our German keeper did really well to turn his effort round the post. A clean sheet and the three points were within our grasp.There were to be no more chances for either side, as our fizzing first half show was enough to grab us the points, and we had the win that helped us keep pace with the top four spots.A good day at the office, and encouraging for us to keep the clean sheet.Onward to our next game versus Bournemouth on Wednesday. Good work Gunners!