Ireland’s Six Nations hopes take potentially devastating blow after Johnny Sexton injury

Ireland are staring down the barrel of starting their Six Nations campaign without Johnny Sexton.

Sexton is a doubt for Ireland's tournament opener against Scotland on February 4 after being taken off injured in only his second game back for Leinster after a month on the sidelines. The fly-half was hauled off just 22 minutes into the province's Champions Cup clash against Castres in Stade Pierre Antoine on Friday night. He kicked a conversion and a penalty before being taken off as a permanent substitute, citing a tightness in his calf. He was replaced by Ross Byrne. Before returning against Zebre in early January, the number 10 had not been seen on the pitch since exiting the fray early during Ireland's defeat to the All-Blacks in the Aviva Stadium. He had not featured for the Blues during the festive period as he was nursing a hamstring injury. With just two weeks until the Six Nations kick off, these fresh injury concerns could give Joe Schmidt a headache when it comes to selection time.