Chelsea's 5 Worst Summer Transfer Deals in the Last 10 Years
It's been a productive summer in the transfer market for Chelsea.
Jose Mourinho has strengthened his squad with the addition of Diego Costa, Filipe Luis and Cesc Fabregas, while the Blues have recouped considerable funds with the sale of Romelu Lukaku and David Luiz for a combined £78 million.
Of course, big-money signings are not always a recipe for success—something the Blues are only too aware of.
Indeed, things haven't always been so merry for Chelsea when it comes to transfers. In the past decade, for every success story, there has been a failure.
Bleacher Report takes a look at the top five.
Jose Mourinho thought he was getting a bargain when he signed Khalid Boulahrouz for £7 million from Hamburg in August 2006.
The Holland international seemed to slot in seamlessly at Stamford Bridge, too, performing well in his first few appearances.
However, as time wore on, Boulahrouz suffered a loss of form that became all too evident with a poor display against Tottenham Hotspur at White Hart Lane.
Robbie Keane gave Boulahrouz a few nightmares after Chelsea's 2-1 defeat, and he never fully recovered in a Chelsea shirt, struggling to become a consistent presence at the back.
He was loaned to Sevilla the following season before being sold to Stuttgart.
Once one of Europe's most feared strikers, Andriy Shevchenko arrived at Chelsea in the summer of 2006 with a formidable reputation.
However, time had caught up with Sheva.
Having paid £30 million for his services, it soon became clear the Blues were sold a dud.
Shevchenko seemed to have lost more than a yard of pace. He struggled to adjust to life under Jose Mourinho and was largely a peripheral figure.
There were moments of brilliance, notably a brace against Aston Villa on Boxing Day 2007. However, on the whole, his Chelsea career was a major disappointment given the success he had previously enjoyed.
Asier del Horno
With Wayne Bridge struggling to return to full fitness from a broken ankle, Chelsea looked to Asier del Horno to beef up their options at left-back in 2005.
Again, the Spaniard was one of those who arrived with a good reputation. He had impressed at boyhood club Athletic Bilbao, where he had risen through the ranks.
After an encouraging start, Del Horno struggled to maintain form in the Premier League, and it soon became clear things were looking bad for him at Stamford Bridge.
It all came to a head when a young Lionel Messi tormented him in a Champions League encounter. Del Horno saw red as Chelsea lost the game 2-1.
That fixture came in February, and Del Horno featured just nine more times for Chelsea before being sold to Valencia in the summer of 2006 for £4.8 million—a significantly lower fee than the £8 million Chelsea paid for him.
With big transfer fees come big expectations.
Shaun Wright-Phillips had the first, but he never quite lived up to the second in a Chelsea shirt.
It was always going to be a gamble when Chelsea paid £21 million for Wright-Phillips in 2005—and it proved one that never paid off for Jose Mourinho.
Slight of frame, yet quick off the mark and skillful, Wright-Phillips had looked an exciting player for City in the days before Sheikh Mansour's billions transformed the club's fortunes.
While he had been the star of a relatively smaller team by comparison, SWP rather blended in with the big names at Chelsea, rarely standing out enough to make an impact.
As you would expect, there were moments of brilliance, but he never quite made the grade.
City bought him back from Chelsea three years later in 2008 for a mere £9 million.
Left-backs—who would have them?
Chelsea have had their fair share of failures in the position in more recent times, so the club's board can be forgiven if they fear the worst whenever the manager suggests a bright new thing that he has had scouted.
The problem has been Ashley Cole.
The Englishman was such a fine player during his Blues career that anybody hoping to challenge him was often left out in the cold.
Yuri Zhirkov was brought in for £18 million from CSKA Moscow with the remit of being Cole's challenger.
Like all the others, he came up short.
Zhirkov was no match for Cole, which meant Carlo Ancelotti tried to integrate him further forward in a left-sided midfield role.
That didn't work, either.
After two seasons of frustration, Zhirkov eventually departed for Anzhi Makhachkala.
The Russian started just 16 games in the Premier League for Chelsea.
Garry Hayes is Bleacher Report's lead Chelsea correspondent. Follow him on Twitter @garryhayes