Who will take the crucial fly-half position for the British and Irish Lions?
That's one of the tough decisions that coach Warren Gatland has to make over the coming months and the issue raised plenty of debate on this week's live Rugby Club Special.
Scott Hastings, Will Greenwood, Shane Horgan and Scott Hastings all agree that one man stands head and shoulders above the rest but say the autumn Tests and Six Nations will give Gatland a better idea of the pecking order.
"I think Johnny Sexton is considerably ahead of anyone else," said Shane Horgan, who toured New Zealand with the Lions in 2005.
"His passing game is remarkable. Then couple that with his running game, I think he is the only fly-half at the moment who poses a really strong threat up tight while maintaining the ability to move the ball wide.
"I know Rhys Priestland is a great running threat but I don't think that at the same time that he is running that he can move the ball. Priestland will attack flat and he will run flat or he will stand deeper and throw the ball wide. Sexton can do both.
"What Sexton also brings to the game is a massive defensive potential. He closes down that channel. Whatever level of rugby you are playing you are always looking to go down that 10 channel, and think that it's a little bit weak.
"Not when Jonny Sexton is down there. The only thing that is stopping him from being at a complete different level to anyone else is that there are a few worries about his consistency kicking the ball off the ground."
Scott Quinnell agrees with Horgan, but says there is also a place for a utility back who can cover multiple positions, as well as fly-half.
"I think Sexton would start in a Test match today but then you have a look at the likes of Priestland, then you have Toby Flood and Dan Biggar who is playing well," said Quinnell whose 1997 tour to South Africa was cut short by injury but was one of the key players in 2001 in Australia.
"Then you have James Hook who is playing in Perpignan and he could be the third fly-half. Gatland is only taking 34 players on tour - so I think one of those 10's will be a Hook-type player who can play 10, 12,13, 15."
Other players to have thrown their names into the hat are Jonny Wilkinson and Charlie Hodgson. Both have retired from international rugby but could they still catch Gatland's eye?
Scott Hastings, who helped the Lions last beat Australia in 1989 and who also toured with the Lions in 1993 to New Zealand, feels that Hodgson may have an outside chance but does not believe there is a place on the plane for Wilkinson.
"As far as I am concerned Wilkinson is not playing - that would be going backwards. It is up to Gatland to pick his style of rugby and I think he will go for Sexton and then Priestland as well.
"I think it is all about consistency and controlling the game. I think Hodgson has undoubtedly played the better rugby of all the fly-halves in the mix.
"However, I think as you go into the autumn series that is where you put your marker down and how you command through the Six Nations. The guys in the shop window during the Six Nations will have the bigger chance to show themselves.
"I like what Shane has been saying about Sexton - he is also a great distributor of the ball but he also runs some great lines and angles and has a great boot on him - although the one question mark is over his place kicking."