Leo Cullen staying positive but one number suggests we should be concerned about Johnny Sexton

Johnny Sexton is Ireland's most important player.

Robbie Henshaw is terrifying with or without the ball, Jamie Heaslip is considered among the best in the world, the front-row have the potential to start for the Lions, Devin Toner is a leader and Simon Zebo is in the form of his life. But they are an amorphous green blob without the Leinster fly-half their to cajole, scheme, organise and inspire. That's why the sight of Sexton limping off after 22 minutes of Friday night's draw with Castres was so difficult to watch. Leinster all but secured their home quarter-final in the Champions Cup in France, but the welfare of Sexton is of critical importance heading into the Six Nations. https://twitter.com/SportsJOEdotie/status/822584496990064642 Ireland kick-off with a tricky trip to Murrayfield and Joe Schmidt will want his lieutenant on the field, he will not want to face old pal Vern Cotter without Sexton's hand on the tiller. Leo Cullen tried to reassure people after the match, but his honest take on Sexton's suspected soft tissue injury were not particularly reassuring. “He just had a bit of stiffness in his calf,” he told reporters. “We’ll see how he presents. “Just a bit of tightness. But again, when he feels that, he was almost there making the call himself. And we obviously go with that. It’s obviously very early days, so we’ll see, get a scan and know exactly what extent there is there.” Sexton will likely meet up with the rest of the Ireland squad at Carton House this weekend but a season delayed by shoulder rehabilitation and interrupted by hamstring injuries does not make us hopeful. In fact, of Sexton's NINE games for province and country in an injury-affected season he has finished just one. While he played 79 minutes of his first game back against Ospreys, it was only the Cardiff game that followed which saw him complete the 80 minutes. He saw 68 minutes action versus Munster but since the attritional Tests against New Zealand (the second of which he lasted just 17 minutes) Sexton has failed to finish a game. Being blatantly targeted by the likes of Francois Steyn does not help, but it is hard to be too hopeful when Sexton has racked up just 460 minutes of rugby this season. That is 385 for Leinster, in seven games, and just 75 for Ireland. Here is hoping he adds another 80 in Murrayfield on February 4th.