The 31-year-old Army doctor, now fully recovered from groin and Achilles injuries, was recalled yesterday by national selectors desperate to restore some authority to a side that under-performed in its two early-season Tests against Australia and Italy.
Wainwright, who relieves Gregor Townsend of the captaincy, skippered Scotland in New Zealand last summer but sacrificed the first half of the current campaign to undergo surgery on his various ailments. He returned to action with Watsonians, his Edinburgh-based club, just before Christmas and then impressed with his displays for Caledonia in the inter-district championship. His return to the back row will give the Scots far greater presence on the pitch but the real benefit may well be felt in the dressing- room, where he was an inspirational figure during the 1996 Five Nations.
The other changes to the side that struggled to beat Italy last month see Peter Walton restored to the loose unit alongside Wainwright, Doddie Weir - back in the engine room at the expense of Damian Cronin - and Gary Armstrong, in residence once again at scrum-half. Armstrong's appearance ensures a battle royal with Robert Howley, the gifted Welsh half-back, on Saturday.
With Townsend partnering Scott Hastings in the centre, Craig Chalmers continues his chequered career at outside-half. That may not please the Lions managerial contingent who make the trip to Edinburgh - they see Townsend as their chief playmaker against the Springboks and would prefer him to be given his head at stand-off in the coming weeks - but the Scots believe they have decided on their optimum line-up.
In total, seven English-based players will take the field for the Scots. That number is likely to rise before very much longer as Kenny Logan, the Stirling County wing, is being linked with a move to Saracens.
The Welsh, meanwhile, trained in Cardiff yesterday and did not escape without a number of injury scares. Howley retired midway through the session with hamstring trouble while Scott Gibbs withdrew after suffering more pain with the knee he injured in last weekend's victory over the United States. Two replacements also gave cause for concern: Gwyn Jones took no part in the session because of shoulder problems, while Craig Quinnell was virtually a passenger because of a hamstring injury. However Kevin Bowring, the coach, said he was confident all four would be fit to fly north tomorrow.
Phil Greening, England's reserve hooker and a hot tip to make the Lions party despite his lack of international experience, is to stay at Gloucester. Greening has been chased hard all season by a clutch of big-spending clubs, notably Wasps.
SCOTLAND (v Wales, Murrayfield, Saturday): R Shepherd (Melrose); A Stanger (Hawick), S Hastings (Watsonians), G Townsend (Northampton), K Logan (Stirling Co); C Chalmers (Melrose), G Armstrong (Newcastle); D Hilton (Bath), K McKenzie (Stirling Co), M Stewart (Northampton), G Weir (Newcastle), A Reed (Wasps), P Walton (Newcastle), R Wainwright (Watsonians, capt), M Wallace (GHK). Replacements: D Stark (Melrose), R Eriksson (London Scottish), B Redpath (Melrose), S Munro (GHK), T Smith (Watsonians), G Ellis (Currie).