But Hull had to wait for the result from Vicarage Road as Watford lost 2-1 at home to Leeds in a game delayed by 16 minutes in the first half by an injury to goalkeeper Jonathan Bond.
The Tigers had trailed to a goal by substitute Fraizer Campbell four minutes after the break. But Proschwitz, a half-time substitute, guided the ball home from a cross by Stephen Quinn with 57 minutes gone and three minutes later McShane got his foot to a Robbie Brady corner.
Hull fans ran on to the pitch when referee Keith Stroud awarded a late penalty for Ben Nugent’s push on David Myler but David Marshall saved Proschwitz’s spot kick. Cardiff immediately went down to the other end and made it 2-2 when Abdoulaye Faye handled and Nicky Maynard sent David Stockdale the wrong way.
At the time, Watford were drawing 1-1 with Leeds and would have gone up with a winner. But Ross McCormack’s injury-time lob gave Leeds a 2-1 win. As a result, Watford had to be content with the play-offs after a game which saw them lose Bond, who had replaced Manuel Almunia before kick-off, to a neck injury which required hospital treatment. After the 16-minute delay Poleon scored when a mix-up between debutant goalkeeper Jack Bonham and Joel Ekstrand saw the defender try to hook a bouncing ball clear, Poleon scoring a simple tap-in.
But Akechi Anya made up for his role in the keeper’s injury when he cut in from the right and fed Almen Abdi on the edge of the area and he fired into the top corner to make it 1-1. McCormack then won it for Leeds, to Watford’s despair.
At the other end of the table, Peterborough were relegated after losing 3-2 at Crystal Palace and Wolves also went down following a 2-0 defeat at Brighton. Palace secured fifth place with goals from Glenn Murray, Kevin Phillips and Mile Jedinak. Peterborough had led twice through Lee Tomlin and Nathaniel Mendez-Laing. A Kazenga LuaLua double after nine and 39 minutes earned Brighton a 2-0 win to give them fourth place and a play-off spot as Wolves went down to League One with Peterborough and Bristol City.
Barnsley led twice at Huddersfield and, despite being pegged, back did enough to stay up with a 2-2 draw. Chris O’Grady and Jason Scotland twice put Barnsley in front but Jermaine Beckford and James Vaughan scored the equalisers.
Leicester sneaked into the play-offs with a 3-2 win at Nottingham Forest with goals from Matty James, Andy King and Anthony Knockaert.
Forest, who scored through Simon Cox and Elliott Ward, lost out along with Bolton who were held 2-2 at home by Blackpool.
Sheffield Wednesday made sure of their status with a 2-0 home win over Middlesbrough thanks to goals from Steve Howard and Leroy Lita and Derby beat Millwall 1-0 with a late Conor Sammon goal.
Charlton defeated relegated Bristol City 4-1 with Yann Kermogant (2), Jonathan Obika and Johnnie Jackson getting the goals.
Burnley defeated Ipswich 2-0 with goals by Junior Stanislas and Martin Paterson. Birmingham drew 1-1 with Blackburn with the goals coming from Ravel Morrison for the home side and Jordan Rhodes.