The afternoon didn’t go as planned, but it shouldn’t take away from a monumental achievement. He joins a list of only other 14 Owls players to have achieved the feat.
The first of those 400 appearances came as Palmer made his Wednesday debut in midfield, in an August 2010 League Cup match against Bury.
The Owls won 1-0 thanks to a Giles Coke winner - but who else played in the match - and which two future Wednesday players featured for the opposition?
Here’s a run through memory lane.
1. Nicky Weaver
A Sheffield-born keeper of huge repute with the likes of Charlton Athletic and in particular Manchester City, Weaver joined the Owls on a permanent basis in 2010 after a loan stint in 2005/06. Went on to play for Aberdeen briefly. Came back to Middlewood Road in 2014 as keeper coach and is currently head of academy goalkeeping. | Getty Images
2. Tommy Spurr
A good friend of Palmer, Owls academy graduate Spurr made over 200 appearances for Wednesday before moving on to Doncaster Rovers in 2011. Blackburn, Preston and Fleetwood were his other clubs before retirement in 2019. Now a school teacher in Lancashire. | Getty Images
3. Darren Purse
Made 61 league appearances for Wednesday across two seasons, mostly as captain. Left in 2011 and went on to play for Millwall, Yeovil, Plymouth and Port Vale before a stint in Finaldn with IFK Mariehamn and a long list of clubs in non-league. Now in coaching, building a promising career with Cardiff u23s. | Getty Images
4. Daniel Jones
A youngster back in 2010, Jones was a bit-part in his time with the Owls before moving to Port Vale in 2013. Had success at Chesterfield and Notts County before falling into non-league. Last seen playing for Longford Town over in Ireland. | Getty Images