Middlesbrough are real dark horses this season.

After a bitterly disappointing campaign last term the expectation was that the Teessiders could be facing another battle in the bottom half of the table.

Instead, they're pushing themselves into top six contention.

While Neil Warnock is building a decent squad, it's a far cry from years gone by when the club have splashed the cash on big-name arrivals.

But who are Middlesbrough's most expensive signings to date? We took to Transfermarkt to compile the top eight.

After winning the Champions League with Juventus the world was shocked when the Italian moved to the Riverside Stadium.

Ravenelli made an immediate impact by scoring a hattrick on his league debut against Liverpool, before scoring another 16 over the course of the season.

The Italian now works as a pundit and aspires to continue his career in management.

The Dutch midfielder arrived at the club in 2016 after they secured promotion to the Premier League.

A popular figure among supporters, De Roon will be most fondly remembered for his headed goal against Manchester City at the Etihad Stadium and those celebrations that followed.

After suffering relegation De Roon joined Atalanta where he's now featuring in the Champions League.

A player who is one of the least popular to sign in recent years.

Despite his obvious talent, Braithwaite rubbed supporters up the wrong way with his lack of commitment to the club which saw him leave the club on loan, and then on a permanent deal.

Now with Barcelona, fans at the Riverside are rubbing their eyes in disbelief as they certainly didn't see a future with Lionel Messi in his future based on his performances.

A striker who played a key role in helping the club to promotion in 2016.

Rhodes scored some crucial goals without ever really being prolific - an issue that has plagued him since leaving the Riverside Stadium.

Now with Sheffield Wednesday, the frontman is struggling to recreate the form that he showed before heading to Teesside.

The late star was the beating heart of Middlesbrough's most successful team in recent years.

Ehiogu was part of the Carling Cup winning side as well as featuring regularly on the road to the UEFA Cup final in 2006.

Value for money on the pitch, and a class act off it.

Middlesbrough's gladiator perhaps wasn't the most gifted player to feature at the Riverside Stadium, but he knew how to make an impact.

Responsible for two of the most celebrated goals in the club's history, Maccarone helped the Teessiders through the UEFA Cup quarter-finals and semi-finals with last-gasp goals.

Now retired, Maccarone can look back on his status as a cult hero with pride.

'Boro's goal-machine' was one of the biggest transfer flops in the club's history.

After smashing them home for fun in the Eredivisie, Alves was expected to hit the ground running be the club's solution to their goalscoring woes.

That didn't happen and he left with his tail between his legs before retiring in 2013.

Middlesbrough's most expensive signing is still at the club.

While Assombalonga perhaps won't be recognised as Middlesbrough's best-ever striker, there's no doubting the consistency of his scoring record.

It's likely that fans won't appreciate what he contributed until after he moves on, which is a shame.