What are the clues that a player is finished? How do you pick up an experienced bargain? In the next part of our Changing Face of Scouting series, with clubs lining up January transfer targets, experienced scout Rob Mackenzie explains how to identify ageing players on their way out and those who still have plenty to offer…
The sight of Ryan Giggs scoring for Manchester United against Everton at the age of 39 or the 40-year-old Francesco Totti still wowing his adoring crowd at Roma could convince anyone that quality is timeless. Class, as they say, is permanent.
But for every player able to sustain such levels well into their 30s, there are many others who are a fading force while still eligible to go on an 18-30 holiday. Identifying whether a player falls into the first category or the second is critical for any scout.
Spot the big name available on a free transfer who is still capable of performing and a fortune can be saved. Award a lucrative contract to a player whose legs and motivation have gone and it can prove an expensive mistake instead.
But there are clues that can help clubs to make the right decision. When newly-promoted Leicester signed a 34-year-old Esteban Cambiasso in 2014, it wasn't because they were star-struck. Rob Mackenzie and the rest of their scouting team had done their homework.
"People might have had the idea that Cambiasso was over the hill, but his profile didn't reveal that at all," Mackenzie tells Sky Sports. "The reality was that he had played in 80 per cent of Inter's matches in his final season at the club.
"That suggested he was still doing the business. When we delved deeper into his character, the references were spot on. I remember the first day that he trained with us, as there was a real buzz around the training ground.
"We even had players who were injured and in the process of doing rehab ask if they could take their exercise bikes pitch side just so they could watch him in his first session with the club.
"Upon meeting him, Cambiasso was the one quizzing us on our fitness preparations. It was clear this was a driven individual who wouldn't want to have the black mark of a relegation on his CV let alone sit on the sidelines. It proved to be a key signing for the club."
Cambiasso's track record proved significant. Having averaged 31.5 Serie A appearances throughout his 10-year stay at Inter, the Argentine duly featured regularly for the Foxes - making 31 appearances as Nigel Pearson's side beat the odds and the drop.
"The robustness of a player's profile is hugely important," adds Mackenzie. "Playing regularly is indicative of many things. It doesn't merely suggest that they avoid injury but also that they do what the coach demands and approach their work properly.
"Napoli's Jose Callejon is a nice example. At the age of 29, he has played over 3,000 minutes in each of his previous three seasons despite playing for two very different managers and coupled with that he has also scored six or more every year since 2010. When you consider those things it wasn't a big surprise to see him score 13 and assist 13 last season. He's on course to do the same again this season too.
"These are the types of things that become particularly important as players get older and their risk of injury increases. Miroslav Klose is someone whose record shows that he could be relied upon - he played at least 30 games for club and country for 16 consecutive seasons. That impresses scouts.
"I've never been too far away from trying to sign him, both previously and also more recently. We wanted him at Leicester upon promotion in 2014 but he chose to sign a new contract with Lazio and he went on to score 16 that year. He decided to retire in November 2016, but if he'd decided to keep playing his record suggests that he could have still made a meaningful contribution at the right club."
While minutes are of paramount importance for defensive players - Mackenzie cites the example of Timmy Simons who played over 4000 minutes across five competitions last season at the age of 38 - forwards actually have more leeway because of their role.
"Consecutive minutes are not always such an issue for forwards because the position does not always demand so much running, depending on the system," he explains. "Of course, there's also the prospect of making a significant impact as a substitute as coaches seek to change games from the bench, and they typically change strikers when they do so.
"So while strikers might peak earlier, that doesn't rule out the possibility of them playing a key role within the squad. Kevin Phillips, Henrik Larsson and Claudio Pizarro are all examples of players who have been bargain signings even when they were past their peak."
What's clear is that it's not as simple as knowing that a player's legs have gone. Even then it depends on the role in the squad for which he's been earmarked. But if the circumstances are right, a veteran supposedly on the way down can prove a priceless acquisition.