Greig Tonks (Edinburgh)

Edinburgh was brought to Edinburgh three seasons ago as a full-back/fly-half, but had to bide his time before making his debut in the playmaking role for the capital club. Since then he has established himself as a solid all-rounder, and could probably be considered the safe option at No.10. He has also played alongside Greig Laidlaw, so the pair could be expected to slip back in as an established half-back partnership. Against that, although he has been on the fringes of the Test scene for a couple of years, he has won just one cap - against Samoa in 2013 - and that has to be a drawback. Verdict: Safe, but maybe too safe.

Peter Horne (Glasgow)

Horne was Scottish rugby's coming man a couple of seasons ago. However, after suffering a hand injury he was usurped by Edinburgh centre Matt Scott and has never quite made it back to the front of the queue. Capable of moments of brilliance - his Heineken Cup wonder try against Northampton became a YouTube hit - but he can also drift out of game a little. He came on as a replacement against France earlier this month, but then dropped out of the squad for the Wales game the following week. Primarily a centre, he impressed at fly-half for Glasgow against Ospreys last weekend and is probably closest to Russell in playing style. Verdict: Must be in with a strong shout.

Stuart Hogg (Glasgow)

Hogg has been in dazzling form at full-back in this year's two Six Nations to date. Nobody doubts that he has the raw footballing talent to play at fly-half, as he filled that role in his younger days at Hawick and was given a run in the position on the Lions tour to Australia two years ago. There is no question that he could make a decent fist of the job, but the greater concern is that his abilities as a broken-play runner would be wasted in the playmaker's berth. His kicking from hand can sometimes be suspect as well. Verdict: Likely to be told to stick to the day job.

Matt Scott (Edinburgh)

Former caretaker Scotland coach Scott Johnson has showered Scott with praise, comparing him to New Zealand legend Ma'a Nonu. However, although Scott was another talented player who grew up playing fly-half, he has never occupied the berth at the top level. Scott missed the first half of the season with shoulder problems and has only recently begun to show signs of the abilities that marked him out as such an exciting prospect a few seasons ago. All in all, he probably needs and deserves more time to get the confidence and consistency back in his game, but he would certainly not let Scotland down. Verdict: The outside bet.

Greig Laidlaw (Gloucester)

The Scotland scrum-half and captain made 10 starts at fly-half for his country in 2012, having only just established himself in the position at Edinburgh. Laidlaw is still well capable of switching between the two half-back positions, and the respect in which he is held by his Test team-mates has to be a point in his favour. Against that, he is in effective and impressive form at scrum-half and has made it clear he is happy to stay there. A brilliant and wonderfully competitive all-rounder, he has admitted that he is not at the front of the queue to take over from Russell. Verdict: Could certainly do a job - but would probably prefer not to.