The two will lock horns when Leinster welcome Munster to the Aviva Stadium on Friday night with Sexton desperate improve on a World Cup record that saw him miss seven on his 11 kicks at goal in the opening two matches.
But the Leinster man can prove he deserves the starting berth when the 2012 RBS 6 Nations kick off.
"Obviously, he didn't have the World Cup he wanted, but there was no sign of that since he came back," said Murphy.
"He's been fantastic. Possibly, there was a little bit of doubt in his mind over there. I don't think his confidence has taken a dent though.
"Since he's come back he's been working hard, but no harder than he would have had he been at 100 per cent over there. He's fine and I have no doubt he will bring it on against Munster."