#1 Coventry City
Out of all former Premier League sides, Coventry City has fallen the hardest. They are currently in the not so glamorous surroundings of League Two. Doing well there, sitting 3rd, but not where you would expect a club of their stature to be.
Coventry had five seasons in League One before eventually dropping down a division. They had nine consecutive Premier League seasons until relegation hit in 2001. Before that, they had been in the top flight since 1967/68. Considering the current state of things, it's funny to look back and note that Manchester City actually got relegated as well in 2000/2001. Oh, how differently things have worked out for the two.
After spending a decade in the bottom ten of the Premier League, Coventry also mostly settled for bottom half finishes in the Championship. An 8th place finish in 2005/06 was the highest they could achieve. And much like it was in the Premier League, where they flirted with relegation multiple times, their luck also ran out in the second tier. Relegation came in 2011/12 following a 23rd place finish.
In League One, the story was the same. Coventry formed a club that mostly finished in the bottom half, and last season another 23rd place finish dropped them to League Two. It's a bizarre sight to see them there.
Coventry still plays at the Ricoh Arena, which was opened in 2005. Its capacity is over 32 500, which is twice as much as most League Two clubs. There are three clubs in the league whose home stadium doesn't even hold 6000 people.