Gregor Townsend will become Scotland's most capped player at the Millennium Stadium on Saturday.
Townsend will be winning his 66th cap, overtaking the mark set by Scott Hastings, and the main focus will surround Castres playmaker, so often an enigma in a Scottish jersey.
Townsend will celebrate alongside another member of the 50-cap club in Kenny Logan.
Doubts remain over his best position, or even whether he should be in the Scottish team at all. But Townsend remains Scotland's most potent attacker, and McGeechan believes the 28-year-old is the best fly-half available.
Logan is the only change made by the coach for this weekend's closing trip to Cardiff from the side defeated by France.
The Wasps winger starts for the first time in over 12 months, winning his 56th cap after just two replacement appearances in this season's competition.
Injury and poor form ruled him out of action during the autumn internationals but he returned to the bench for Scotland's defeat in Dublin last month. Glenn Metcalfe steps down to the subs' bench.
Scotland team: B Laney (Edinburgh); K Logan (Wasps), J McLaren (Glasgow), J Leslie (Northampton), C Paterson (Edinburgh); G Townsend (Castres), B Redpath (Sale, capt); T Smith (Northampton), G Bulloch (Glasgow), M Stewart (Northampton), S Murray (Saracens), J White (Glasgow), M Leslie (Edinburgh), B Pountney (Northampton), S Taylor (Edinburgh).
Replacements: R Russell (Saracens), G Graham (Newcastle), S Grimes (Newcastle), J Petrie (Glasgow), G Beveridge (Glasgow), D Hodge (Edinburgh), G Metcalfe (Glasgow).
