You could almost argue that it didn't, or at least not yet. In his first season he saved City from relegation, in his second he achieved what nobody else has done before in managing the Tigers to promotion to the Premier League, in his third he kept the team up, and in this his fourth was in contention to do the same again.
However, things have undeniably been on the slide for some time. Losing Marlon King and Jimmy Bullard took away the side's attacking threat and Brown responded to heavy defeats against Sunderland and Manchester City in December 2009 by playing tighter, more cautious tactics. We whimpered through the second half of last season with only one win.
Brown recognised this wasn't the way to go and addressed the problem by making a point of signing players who would add goals to the team: Seyi Olofinjana, Jozy Altidore, Stephen Hunt, Kamel Ghilas, Jan Vennegoor of Hesselink, Amr Zaki. On the flip side, City's defence was weakened by the sales of Michael Turner and Sam Ricketts and replacing them on the cheap.
This is where some of Brown's tactics over the last few months haven't made sense. Many of his attacking signings have been left out of the team - sometimes on the back of good performances - when Brown has reverted to trying to play more cautiously. A loss of nerve, perhaps? With a defence that so easily leaks goals, taking away our attacking threat would only result in defeat.
Brown actually played one of his most courageous hands in his last match in charge and it very nearly paid off. He picked players who could, and did, cause Arsenal's defence problems, and even stuck with them for much of the second half after having a midfielder sent off.
This makes the timing of his departure strange. Was it already decided before the Arsenal game, as rumours on Friday and bookies' odds being slashed suggested? Have the board delayed the action until the desired replacement was secured? I will be surprised if Brian Horton remains in charge for the rest of the season, and wouldn't think that Adam Pearson would have preferred that option to giving Phil Brown his chance until the very last.
There is another possibility, which is that Brown has been placed on gardening leave for some disciplinary reason. However, as there is no evidence for that I won't entertain the idea further, especially as results alone do merit his removal from the position, and they are quite clear:
One win in our last 15 games.
4 successive defeats.
No away win in over a year.
39 points from our last 59 league games. That would average 25.5 points over 38 games: Only Derby, Sunderland twice and Watford have finished a Premiership season with fewer points than that.
Despite all the effort shown against Arsenal, Manchester City and Chelsea, we're 2nd from bottom because of the points dropped against Wolves, Sunderland, Birmingham, Fulham, Portsmouth, Burnley, West Ham and Blackburn - all unbeaten by us this season.
Phil Brown's side won just 2 points from the final 9 games last season. The board have decided to twist in the hope of better this time - a gamble they felt they had to take.
He didn't always help himself, but Phil Brown deserves more credit than the media and people away from the club have given him or ever will. The fans will always remember what he did for our club.
As he famously sang: "I don't want to go home, this is the best trip I've ever been on." We have Phil Brown to be eternally grateful to for helping us take this trip. Now somebody else must "step up to the plate" to get us back on course and make this remain our home.