Back in the day, the first time you'd get to see what a new player was like, was when he turned up for his debut. You might have seen him play against your team last year - but generally, it was difficult to really scout a new face.
Not since the advent of the television age, mind - and with YouTube, it's even easier. The chances are that you've heard of the guy you're getting at the very least - you might even have watched him extensively before or signed him on Football Manager.
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But it doesn't always work out how you plan. We asked our Twitter followers for the players that they couldn't believe their luck at signing - did they work out, too?
The good
His one season in English football was as classy as you'd expect. Did he still have it? Hell yeah, he still had it.
Let's hope he didn't do the same for Robert Lewandowski in 2010.
Cardiff paid £350,000 Whittingham and got 457 games out of him. That's under £800 a match. Fantastic value.
Sir John Mills, as one Hereford fan on the FFT team knows him.
Kids today will never understand quite how great David Batty was, for a number of reasons. The first being that David Batty never gives interviews anymore.
The early 2000s were an incredibly exciting time to be a Bolton fan. Who are you going to sign this window? Jay-Jay Okocha? Youri Djorkaeff? Rivaldo? Fernando Hierro? Never put anything past Big Sam.
More Jay-Jay Okocha love, this time from a Hull City fan. You can't help but get excited if you sign that guy.
He came back though, Alan!
Good to see some love for Veron from Manchester United fans. A fantastic player at his peak.
Two seventh-placed finishes and half of Portugal uprooting to the Midlands. It was a success, we reckon.
The bad
Scientists are still trying to explain the demise of Fernando Torres.
The career of Edgar Davids is really quite incredible. Played at the absolute pinnacle of the game in sunglasses, was a poster boy for Nike and when you thought he was retiring back at Ajax... he turns up at Selhurst Park... before going to manage Barnet. Blimey.
He looked good at Barcelona. He did not look good at Tottenham.
After scoring his first goal for the Baggies, Anelka performed a quenelle salute, which earned him a five-match ban due to its antisemitic connotations. Then he announced he was terminating his contract, much to West Brom's surprise.
At least it was a free transfer, though.
Those four goals in his first month, though... they were good.
The undecided
Xherdan Shaqiri being decent but having little input in Stoke staying up is a little like Xherdan Shaqiri being decent but having little input in Liverpool winning the title. Hard to quantify if he's been a good signing anywhere he's gone, really.
OK, so Andrey Arshavin didn't achieve what many Arsenal fans thought he would do. But he did score four goals at Anfield and host a bizarre Q&A on his website where he revealed that he liked bears, considers astrology a science and went 20 years without going to the dentist. Hard to know if he was value for money.
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