Scotland hooker Dougie Hall has lost his battle to be fit to face Italy in Saturday's Six Nations international at Murrayfield, the Scottish Rugby Union announced on Thursday.
Hall, who started in the 38-18 defeat by England last week, has failed to recover from a knee strain suffered at Twickenham.
Ross Ford was named at hooker when coach Scott Johnson unveiled his side to face the Azzurri on Tuesday, with Hall bracketed alongside Glasgow team-mate Pat MacArthur on the bench
But it is the uncapped MacArthur who will be among the Scotland replacements in Edinburgh this weekend for a match where Italy will look to build on their impressive 23-18 first round win at home to pre-tournament favourites France.
"It's a huge honour to have the chance to play for my country," said the 25-year-old MacArthur.
"It's something I've dreamed about since I started playing mini rugby at Ayr and aimed for since I became a professional with Glasgow Warriors."
Meanwhile, flanker Alasdair Strokosch could feature again in this tournament despite breaking a bone near his eye against England.
Strokosch is set to be sidelined for at least four weeks but could be fit to face Wales on March 9 and France the following weekend.
Revised Scotland team (15-1)
Stuart Hogg; Sean Maitland, Sean Lamont, Matt Scott, Tim Visser; Ruaridh Jackson, Greig Laidlaw; Johnnie Beattie, Kelly Brown (capt), Robert Harley; Jim Hamilton, Richie Gray; Euan Murray, Ross Ford, Ryan Grant
Replacements: Pat MacArthur, Moray Low, Geoff Cross, Alastair Kellock, David Denton, Henry Pyrgos, Duncan Weir, Max Evans