Sean O’Brien is absolutely essential to Ireland winning the Six Nations

Sean O'Brien was not quite as chirpy as usual on the referee's microphone during Ireland's 28-19 victory over Argentina.

Listening in to the ref mic in any game involving O'Brien and you will hear the Carlow man, loud and clear. From the opening exchanges to the final dregs, O'Brien can be heard as he gees up teammates, stresses the importance of the next play, yaps at opponents and gives the match officials blow-by-blow accounts of rucks and mauls. For the most part on Saturday, though, he kept his thoughts to himself. At one scrum, with Argentina trying to get a foot-hold in the game, he piped up - "Don't f**king let them in here boys!" Quieter than his standard contribution, but O'Brien's actions reverberated throughout the game. Having done well in the 35-point win over South Africa, the flanker was better again as another southern hemisphere challenger was sent packing. He was an absolute pest to the Argentineans and hounded them for the entire 65 minutes he was on the pitch. Ireland found themselves 13-0 up after 25 minutes but Los Pumas surged forward in the final 10 minutes of the first half. O'Brien came into his own here, spoiling, harrying and hitting bodies aplenty only to spring up and go again. He hounded Nicolas Sanchez on one carry into the Irish 22 and, wrestling the ball loose, Rob Kearney stepped in, poached and the turnover was complete.

Credit: RTE

Five minutes later, with the dressing rooms in sight, O'Brien secured a brutish turnover of his own - outmuscling three men to come away with the pill. Peter O'Mahony was next on the scene to clear some men off and O'Brien was able to cleanly present to Conor Murray. [caption id="attachment_142761" align="aligncenter" width="565"] Credit: RTE[/caption] There were a few decent carries too and one glorious offload that Rory Best just failed to hold onto. CJ Stander made more carries than O'Brien and O'Mahony put together but all three won their fair share of collisions. This will be Ireland's starting back row in the 2018 Six Nations, fitness allowing. It was heartening to see Stander getting back to his dynamic best but O'Brien is the key figure in this Irish back row. He gets through so much work and is truly feared and respected by opponents. He is a tough, tough man to shift too. Breakdown dominance is crucial in the winning of most matches and this is magnified at Test level. O'Brien was one of six Irish players not to miss a tackle in the Argentina triumph but he was the only man to register 10+ tackles without dropping off one or being run over. In fact, O'Brien had 14 successful tackles to go with 12 [and none missed] against the Springboks. He does his job and does it extremely well. Scotland and England look to be the two big threats in the upcoming Six Nations but Ireland will be confident they can top the table. O'Brien is a class act and Ireland will hope he comes through the festive period in similarly good form and, more importantly, good nick.