Once upon a time, the world of football transfers wasn't so organised, regulated and restricted as it is now.

Indeed, prior to it's introduction at the start of the 2002/03 campaign, clubs from the Premier League and yonder could sign and sell players as freely as their hearts desired until the cut-off point of March 31st - a safeguard against teams with little to play for flogging their biggest stars to relegation battlers prepared to pay anything to avoid the drop.

But we now live in the era of the two-window system and the vast majority will argue that we're much better for it; clubs are encouraged to consider longer-term deals, player contracts are far more stable and the money changing hands can be regulated with greater ease.

So in homage to the transfer window, Football Fancast have decided to take a look at Arsenal's worst ever summer signings since it's introduction over a decade ago.

Are these the Gunners' FIVE worst summer buys since 2002?

DENILSON

Denilson

Arsenal fans have a knack of getting excited about young players far too quickly and playmaker Denilson is a perfect example.

Indeed, quite the fanfare surrounded the midfielder when he arrived in north London from Sao Paulo in summer 2006, in no small part due to Arsene Wenger splashing out £3.4million on him (back then, a relatively significant sum) despite making only 13 league appearances for the Brazilian outfit.

To give credit where it's due, Denilson showed enough promise during the early stages of his Gunners career, which reached a climax during the 2008/09 campaign as he amassed three goals and seven assists in 37 Premier League appearances, warranting a new contract at the beginning of the following season.

But he never really surpassed the realms of mediocrity and that extended deal proved to be the turning point, as Arsenal's never-ending curse of continuously crocked youngsters took hold of the former Brazil U17.

He went on to make just 36 more Premier League appearances for Arsenal before spending the remaining two years of his contract out on loan at Sao Paulo; a cyclic end that epitomised how Arsenal gained absolutely nothing from having Denilson on their books for seven years.

ANDRE SANTOS

Andre Sanots

The epitome of a panic buy, Andre Santos signed for Arsenal on the 31st of August 2011 after Arsene Wenger made the surprise decision of allowing first-choice left-back Gael Clichy join Manchester City for £7million.

The Brazil international had always been billed as an attacking full-back in typical Selacao style, but what that truly meant the Gunners only realised after the former Fenerbahce man had turned up in north London.

Indeed, going forward Santos wasn't too shabby. Defensively, however, he was nothing short of a complete disaster and his pot-bellied fitness certainly didn't help matters.

After his first season, managing only 15 Premier League outings, Santos still had the majority of the Arsenal fan base on his side, albeit in more of a novelty manner, similar to Emmanuel Eboue, rather than actual appreciation of his abilities - or lack of, I should say.

But the wing-back soon switched from village idiot to pantomime villain when he committed one of English football's most unforgivable acts - swapping shirts with the opposition at half time, all the more infuriatingly following an abysmal 45 minutes against Manchester United.

To make matters even worse, he swapped shirts with a certain Robin van Persie, who had controversially forced his way out of Arsenal to join the Red Devils just a matter of months prior after refusing to sign a new contract.

As a bog-standard footballer who had just swapped shirts with Judas at half-time in front of a packed Old Trafford, there was no going back for Santos. He made just a handful more appearances before being sent as far away from north London as possible - Brazilian outfit Gremio to be precise.

After his loan spell with Gremio, the now 32 year-old was released. Currently, he plies his trade with Swiss outfit FC Wil.

MAROUANE CHAMAKH

Marouane Chamakh (Crystal Palace)

Marouane Chamakh may have arrived at Arsenal on a free transfer in summer 2010 but he's still easily one of the worst centre-forwards to ever put on a Gunners jersey.

His Emirates career started decently enough, scoring ten times in all competitions by mid-November. That included strikes in the Emirates Cup, the Premier League, the Champions League and the Capital One Cup, as well as the fastest league goal in Arsenal history - just 58 seconds into a 2-0 victory over Wolves.

But that was followed by a disastrously barren run that wasn't ended until March 2nd - a goal against Leyton Orient in the FA Cup. In the meantime, the cumbersome Morocco international had spent prolonged periods on the subs bench and even excluded from the Gunners' matchday squad.

The following campaign, Chamakh managed just one goal in all competitions, which proved to be his last Premier League net for the north London outfit. Barring a brace in an unforgettable 7-5 Capital One Cup comeback against Reading in 2013, the striker spent the remainder of his Gunners days rotting in the reserves and out on loan to West Ham, where he amassed just three appearances without scoring in six months.

The 6 foot 1 forward was eventually allowed to leave for Crystal Palace in summer 2013 without a transfer fee, where he's conjured up just seven goals in two seasons.

SEBASTIEN SQUILLACI

Sebastien Squillaci

One upon a time, Sebastien Squillaci was a decent centre-half. A stalwart at the back for Monaco, Lyon and Sevilla and a 21-cap international for France. Then he moved to Arsenal for £4million.

Despite the difficult task of forging a centre-back partnership with fellow summer 2010 arrival Laurent Koscielny, things didn't start too badly for the now-34 year-old, producing displays that affirmed his reputation as a consistent if somewhat unspectacular and physically anaemic defender.

But soon Squillaci's form took a dip for the worse and he became at fault for several Arsenal concedes - not least including the bizarre incident in the video below, in which he inexplicably head-butted Koscielny to allow Fulham's Diomansy Kamara a free run at goal.

He also came on for an injured Yohan Djourou at half-time as Arsenal held a 4-0 lead over Newcastle, only to somehow allow the Magpies to stage a four-goal comeback in the second half.

That pretty much cemented the theory that Arsene Wenger had been coaxed into buying a dud; a veteran centre-back who had surpassed his peak and couldn't cope with the athletic intensity of the English game.

So by the end of his first campaign at the Emirates, Squillaci was already deemed one of Wenger's biggest transfer failures - but it didn't stop there.

Rather than accepting his shortcomings in gentlemanly fashion and moving on or even look for game-time out on loan, the Frenchman spent the next two years frolicking around the Gunners' training ground - making occasional substitute appearances in the FA Cup and League Cup - until his contract expired in summer 2013.

In addition to his £4million transfer fee Arsenal paid Squillaci £50k per-week, meaning they spent £11.8million on the flopped defender overall. That works out at £340k per Premier League appearance.

PARK CHU-YOUNG

Park Chu-Young

In both footballing and financial terms, Park Chu-Young is arguably the weirdest and worst signing in Arsenal's recent history, described by The Telegraph's John Duerdin as "the worst call to answer since Colin Farrell picked up a New York public phone in Phone Booth and endured a few hours of misery."

He arrived at the Emirates under rather bizarre circumstances; allegedly marching straight out of his hotel room in France and making a beeline for north London the moment he was made aware of the Gunners interest, no-showing his previously arranged medical with Lille in the process.

Arsene Wenger squeezed in a deal with just two days of the 2011 summer window remaining, but soon came to regret how hastily the Gunners had approached the South Korea striker.

Indeed, just one season, a single goal and six appearances later, Arsenal had already written off Chu-Young's £5.5million transfer fee in the club accounts - in other words, proving to the Inland Revenue that he was completely useless, worthless and no longer an asset of any monetary value, like a normal business might write off a rusting company car or a derelict building infested with Ebola-carrying termites.

Overall, the former FC Seoul and Monaco front-man managed just one Premier League appearance during three years at the Emirates - an eight-minute substitute outing against Manchester United - before being released on a free transfer in summer 2014, bringing his Arsenal nightmare to an end.

Aged 30, Chu-Young is now back with FC Seoul, netting six times in 17 appearances since signing for them in March this year.