Scotland host Wales in the Guinness Six Nations at Murrayfield on Saturday.
Here, the PA news agency analyses one of the key duels that will help decide the outcome.
Hamish Watson – Scotland
Position: Flanker
Age: 29
Caps: 37
Debut: v Italy, 2015
Points: 20 (4t)
Height: 5′ 11″
Weight: 16st
Win percentage: 58.10 per cent.
In the year of a British and Irish Lions tour, the Edinburgh flanker could not have started it by making a stronger selection claim than he did during Scotland's Calcutta Cup victory over England – their first at Twickenham since 1983. Workaholic Watson was everywhere, excelling at the breakdown, hitting tackle after tackle and also making his fair share of metres. A total nuisance for any opposition with his all-action style, and a player that excels on the big stage.
Justin Tipuric – Wales
Position: Flanker
Age: 31
Caps: 81
Debut: v Argentina, 2011
Points: 50 (10t)
Height: 6′ 2″
Weight: 15st 7lb
Win percentage: 59.14 per cent
Has been a key part of Wales' armoury for the best part of 10 years. Made his Test debut aged just 22, and despite often finding himself facing fierce back-row competition at international level with Wales, he has delivered one world-class performance after another. A master operator at the all-important breakdown area, his work there has repeatedly put Wales on the front foot, while his tackle-count is rarely short of spectacular and his ball-handling and footwork mean he would not be out of place in the back division. Outstanding player.
