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.
9. Gary Teale
A former Premier League player with Wigan and Derby, Wednesday were Teale’s penultimate club. Retired as a St Mirren player in 2015 with 13 Scotland caps after his stint as caretaker manager was not extended. Was business development manager for a football training equipment company before it went bust earlier this year. | Getty Images
10. Neil Mellor
Son of Wednesday legend Ian Mellor, Neil was the Owls’ most recent 20-goal man before the efforts of Michael Smith last season. He retired aged just 30 with injury problems and now works in the media. | Getty Images
11. Paul Heffernan
A hero at Doncaster Rovers, Heffernan’s spell at Wednesday was brief before a move to Scotland where he played for Kilmarnock, Hibs and Dundee among others. Now coaching in his native Ireland with Bray Wanderers. | Steve Ellis
12. Giles Coke
On as a sub in the Bury clash, Coke left Wednesday in 2015 and went on to play for a number of clubs before finishing up with Grimsby Town last year. Is now coaching with the Mariners. | Getty Images