Promoted Brighton missed out on a chance to secure the title, losing 1-0 at home to Bristol City to a goal, two minutes before the break, from Josh Brownhill. The loss leaves Brighton a point ahead of Newcastle, also promoted, with the final round of games next weekend.
Wednesday's sixth straight win came with a 1-0 victory at Ipswich, thanks to a Kieran Lee goal, and means they cannot be caught by seventh-placed Leeds United.
Third-placed Reading will also be involved in the four-team battle for a place in the Premier League after they beat Wigan 1-0, through an early header from top scorer Yann Kermorgant.
That result meant an immediate return to the third tier for Wigan who join Rotherham United in being relegated to League One next season.
Huddersfield, who had already made sure of their place in the playoffs, fell to a 2-0 loss at lowly Birmingham City, who enjoyed their first win under new manager Harry Redknapp.
Birmingham are now two points ahead of Nottingham Forest and Blackburn Rovers, who both have 48 points and are scrapping to escape the final relegation place.
Read the full article on eurosport.co.uk: Wednesday and Reading secure playoff spots as Wigan go down