Editor's note: The figures in this article do not take into account commissions and salary. Exchange rates at the time of publication are as follows: €1 = £0.84, $1.10.

It's hard to imagine it now, but not everyone loved Liverpool's signing of Virgil van Dijk when it was confirmed on Jan. 1, 2018. Although the fee was in keeping with the percentage of revenue big clubs typically spend on big signings, the raw total seemed shocking. It was €85 million, which shattered the previous record fee for a defender: Manchester City's €58m move for Benjamin Mendy just a few months prior.

Most infamously, the BBC's Alan Shearer slammed the move: "No, he is not worth it at all." The former Newcastle great later went on: "He is good, but £75m? No."

Van Dijk didn't have the kind of pedigree we typically associate with record-breaking moves. He wasn't on every "next big thing" list, he didn't come through any of the Dutch finishing-school academies like Ajax or PSV, and he didn't make his debut for the Netherlands until after his 24th birthday. Two seasons before he moved to Anfield, Southampton had scooped him up from Celtic for €16m. While he was certainly impressive in the Premier League, he wasn't even necessarily in the conversation for "best defender in the world." Hell, he wasn't necessarily even viewed as the best defender in the Premier League.

Skepticism over the fee wasn't just talking for the talking heads, either. The folks at soccer consultancy 21st Club agreed with Shearer. Their player-valuation algorithm takes into account a number of factors -- historical comps, a holistic player rating, and playing characteristics -- to determine an estimated market value for every player. At the time, they rated VVD as a €35.8m player.

Andy Robertson and Mohamed Salah have been two of the best value transfers over the past five seasons. Most of this Liverpool team is in the top 20 for best deals. LINDSEY PARNABY/AFP via Getty Images

All of that, of course, has changed. Liverpool have made two Champions League finals since he arrived, and barring a meltdown of historic proportions, they're going to win their first league title in 30 years. Van Dijk, meanwhile, is the defending UEFA and Premier League Player of the Year, and his arrival directly coincided with Liverpool's transformation into the best defensive team in the world.

Any immediate assessment of a transfer is, therefore, a projection, an educated guess as to how the new player will interact with his new team and his new manager. However, with a couple of years of hindsight, we can assess which deals have worked out and which ones haven't. So, we've joined forces with 21st Club to choose the five best and five worst transfers in the Premier League since 2014-15.

To be as objective as possible, we've created a framework that awards a score to all of the deals:

- 35 percent of the score: the percentage of minutes the player has played for his new club

- 25 percent: the price a team paid versus Transfermarkt's valuation (lower than market value earns a higher score)

- 15 percent: how much the player's rating from 21st Club has improved (or declined) since the deal

- 15 percent: how the player's market value according to 21st Club has changed

- 10 percent: the actual transfer fee (players who cost less are given a higher score)

For purposes of comparison, we're only including players who are still with the team they transferred to and players who cost at least €5 million.

(Oh, and if you're curious: Van Dijk didn't make the cut. He rated as the 52nd-best move since 2014-15, mainly because of how much he cost compared to his market value. However, that value has since risen to €88.2m -- more than the initial fee -- and Van Dijk has become the highest-rated player in the entire dataset.)

The best transfers in the Premier League

1. Andy Robertson, Hull City to Liverpool, 2017 -- Fee paid: €9m (Current value, per 21st club: €98m)

2. Dele Alli, MK Dons to Spurs, 2015 -- Fee: €6.6m (Value: €63m)

3. Georginio Wijnaldum, Newcastle to Liverpool, 2016 -- Fee: €20m (Value: €67m)

4. Mohamed Salah, Roma to Liverpool, 2017 -- Fee: €42m (Value: €119m)

5. Ricardo Pereira, Porto to Leicester, 2018 -- Fee: €22m (Value: €29m)

The headline sounds ridiculous: Little Known Fullback from a Relegated Team With a Bad Defense Almost Immediately Becomes a Starter for the Best Team in Europe. But that's exactly what happened. While Robertson's value has increased FOURTEEN-FOLD since his move to Liverpool -- up to €98m -- what really pushes him up to No. 1 is how well and how often he has played.

Players with improved performance have seen their transfer values increase most sharply, as shown by the cluster of star names toward the top-right corner of the chart. Ryan O'Hanlon / 21st Club

Among all the players who fit our criteria, Robertson's rating has improved the most. Since 2014-15, the only transferred players with more assists than him are Kevin De Bruyne, Alli, Roberto Firmino, Raheem Sterling, Leroy Sane, Son Heung-min, Paul Pogba and Salah. The difference, of course, is none of them are defenders, while Robertson is. In addition to contributing so much in attack, he's a consistent starter for the team that 21st Club rates as the best defense -- and best team -- in the world.

Along with Robertson, Alli and Wijnaldum perhaps speak to an oft-overlooked nugget of transfer-window wisdom: There's value to be found in the lower leagues, even when you're the biggest, richest teams in the world. Both Robertson and Wijnaldum were sold by teams preparing to play their next seasons in the Championship, while Tottenham grabbed Alli from a team that was playing in League One. With the likes of Norwich's Emiliano Buendia and Aston Villa's Jack Grealish performing at a high level for teams that look like favorites for relegation, there should be some opportunities for smart teams to add key contributors for discounted fees this summer.

The other standout factor from this top five is that, well, 60 percent of them play for Liverpool. And it's not just this select quintet, either. Alisson's move from Roma ranks ninth, Firmino's switch from Hoffenheim ranks 11th and Fabinho's transfer from Monaco ranks 16th. On the other end of the spectrum, Bournemouth's purchases of Jordon Ibe and Dominic Solanke rank in the bottom 20 of the transfer score. Both players came from Liverpool.

"Liverpool have become the blueprint for transfer success. They have become the best team in the world by being patient in the transfer market," said AJ Swoboda, managing director for the Americas at 21st Club. "Liverpool's front three cost less than €120m but are now worth closer to €350m. During the same period, their strategy around moving players on has also been smart. [Philippe] Coutinho was sold for around €150m to recoup the entire fees paid to acquire the front three."

At the end of the 2014-15 season, the club had whimpered out of the Champions League group stages, finished sixth in the Premier League with a measly plus-four goal differential, and just sold Sterling to Manchester City. According to 21st Club, Sterling is the best player other than Van Dijk to transfer to a Premier League team since then. Liverpool made up for that loss by adding numbers three through six: Robertson, Alisson, Salah and Sadio Mane, in that order. Wijnaldum (10th), Firmino (13), and Fabinho (18) all rank in the top 20, too.