Maitland missed the tournament opener against Italy with a hamstring problem and has now been sidelined by a foot injury after scoring two tries for his English side Saracens at the weekend.
Harris featured in the 33-20 victory over Italy, but sat out the next two games and has a calf problem.
Scotland are hoping to end Wales' 12-match unbeaten run, and their Grand Slam hopes, and have welcomed back flank Hamish Watson, lock Sam Skinner, prop Willem Nel, hooker Grant Stewart and centre Stafford McDowall from injury ahead of the fixture.
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(Reporting By Nick Said; Editing by Christian Radnedge)
