Victory over Wigan St Jude’s on Saturday was not enough to keep Tuffs in the role, with Acorn still second-bottom of the National Conference premier division.
Rhodes, 30, will stand in as coach, starting with Saturday’s trip to bottom club Wigan St Patrick’s.
A product of cross-city rivals Heworth ARLC, Rhodes began turning out for Acorn after retiring from the pro game in late 2008 due to work and family commitments.
A shoulder problem had also cut short his last season with the Knights, after five-and-a-half years and a club record 113 appearances with his home-town outfit.
Rhodes, the Knights’ Press Player of the Year in 2006, after being part of the team that won the National League One title in 2005, also won six caps for Scotland and had spells at Dewsbury and Sheffield, having started in Leeds’ academy.
Neither Rhodes nor Tuffs were available for comment. Acorn rugby chairman Steve Bromwich said: “We’re fortunate Scott has agreed to steady the ship while we find someone in a position to take the coaching role permanently.”