Although Championship side Birmingham City have underwhelmed in recent years, some of their recruitment has been impressive, especially since Lee Bowyer and Gary Gardner came in.

The likes of Dion Sanderson and Tahith Chong both shone during their time at St Andrew's - and if they had the chance - you would bet the Blues would want to get fresh agreements over the line for the duo who may be available once more this summer.

Matija Sarkic was another superb addition, proving to be an excellent temporary replacement for Neil Etheridge during the first half of the campaign and establishing himself as one of the West Midlands side's best players before he was forced to return to Wolverhampton Wanderers after dislocating his shoulder.

However, there have been those that have been less successful and performed well below expectations during their time at the club - one of several reasons why they continue to find themselves towards the lower end of the table.

We take a look at eight players that fit into this category and reveal where they currently are now.

22-year-old Castillo arrived at St Andrew's last summer but failed to nail down a regular first-team spot during his loan spell away from Premier League outfit Chelsea, making just five senior appearances before he returned to Stamford Bridge in January.

During his time at the club, Bowyer admitted that fitness issues hampered the Dutchman's progress at first and though he did save praise for the left-sided player a little later on, that wasn't enough to keep him at the club for the entire season.

He then dropped down a level and plied his trade at League One side Charlton Athletic for the remainder of the campaign - but barely featured at The Valley either and with this - his future with the Blues looks bleak.

It wouldn't be a surprise if he was available again this summer with the 22-year-old not doing enough to justify a first-team place under Thomas Tuchel.

Croatian Sunjic has remained at St Andrew's - but even he will know deep down that Bowyer's side would probably look to move him on if a reasonable offer came in for his services.

Football League World understands the Midlands outfit were actively looking to move on some of their higher earners including the 25-year-old during the January window - but a move away didn't materialise for him.

Considering they spent around £6.3m on him during the summer of 2019, he has been hugely disappointing but it will be interesting to see if he can thrive if he gets a move elsewhere.

He still has two years left on his contract though, so it may be quite a challenge to sell him during this window unless they are prepared to accept a very modest fee for his services.

You have to feel sorry for Aneke - because he didn't really get a huge chance to shine for Bowyer's side when he was at the club before moving on permanently in January.

Considering he only arrived last year, he didn't even have a full season to shine after initially struggling to make the impact he did for Charlton Athletic prior to his move to the West Midlands.

Scoring 15 times in 38 league appearances for the Addicks during the 2020/21 season, his arrival was an exciting one for the second-tier side considering the forward was already used to Bowyer's methods and was more likely to hit the ground running because of that.

But his spell at St Andrew's was anything but successful, scoring just twice in 18 displays and being offloaded to the Addicks once more in January, recording four goals in nine appearances since his return to The Valley.

After winning promotion with Brighton and Hove Albion as one of their star players, it was a shock to see him reject a new deal at the Amex Stadium and link up with the Blues in 2017.

This looked to be a real coup for the club - but he was unable to replicate what he showed on the south coast and appeared just 36 times during a three-year spell at St Andrew's before joining Wycombe Wanderers.

He spent two years at Adams Park and played his part in helping the Chairboys to reach last month's League One play-off final - but made an error for Sunderland's first goal as he fell to a 2-0 defeat to the Black Cats.

Last week, it was announced he would be joining Sheffield Wednesday on the expiration of his deal in Buckinghamshire and will be hoping to chase promotion once again, with the Owls one of the favourites to fire themselves back to the second tier next term.

The signing of San Jose back in 2020 looked to be a real coup considering the amount of experience he had with Athletic Bilbao under his belt - and was backed to thrive in the English second tier.

But unfortunately, the 33-year-old failed to thrive consistently in the Midlands and this was particularly disappointing considering he didn't just have a decent amount of domestic experience under his belt, but also represented Spain on seven occasions.

He requested to leave the club during the summer of 2021 and was granted that wish as he had his contract terminated early in the latter stages of May last year.

The midfielder has since gone on to ply his trade at Spanish second-tier side Amorebieta back in his home nation, making 28 appearances in all competitions but couldn't prevent them from being relegated straight back to the third tier.

The Senegalese midfielder, who is now 36, arrived in 2017 and looked quite a promising signing on paper after impressing in France as he recorded 14 goals and 10 assists in his previous two Ligue 1 seasons combined before his move to St Andrew's.

Prior to his time in the French top tier, he was also a real asset in the nation's second tier with Angers, getting into double figures during 2013/14 and 2014/15 as he played a big part in getting them to the top flight during the latter season.

However, he didn't score a single goal during his time with Birmingham and only recorded one assist in 42 appearances as he struggled to make a real impact before being released in 2019.

Considering he played a big part under Aitor Karanka when Middlesbrough won promotion back to the Premier League, Clayton was an ideal signing when he linked up with his former boss at St Andrew's back in 2020.

Unfortunately though, he was unable to perform to the standard he did at the Riverside and made just 16 appearances for the Blues in all competitions during his time at the club despite signing a two-year deal with an option for a third.

His contract was terminated early last November and that was no real surprise considering he was frozen out of the first-team squad at that point.

Since then, he signed an 18-month deal at then-League One side Doncaster Rovers but couldn't prevent them from getting relegated as he made just 12 league appearances during the second half of the 2021/22 campaign.

After impressing at Brentford, Jota was tipped to be a key player for the Blues after arriving for a then-record fee believed to be over £6m.

Unfortunately, he was unable to replicate what he showed at Griffin Park as a less prolific figure, though he did earn a move to Aston Villa in 2019 but failed to make a huge impact under Dean Smith either as he left after just one season, having his contract terminated.

He joined La Liga side Alaves shortly after, but only spent one campaign there as well and has been a free agent since last summer, though he should still have plenty of football left in the tank at 31.

At this stage though, it's currently unclear where his next move will be.