The Egypt international has far exceeded all expectations since his arrival at Liverpool, but which other players made similarly massive impacts?
Gareth Bale (Real Madrid)
Arriving at Santiago Bernabeu as the most expensive player in history, much was expected of Bale, and he did not disappoint in his debut campaign. Directly involved in 28 goals in just 27 Liga matches, the Wales international also scored in the finals of both the Copa del Rey and Champions League as Carlo Ancelotti's side won both competitions.
Wesley Sneijder & Diego Milito (Inter)
Signed by Jose Mourinho ahead of the 2009-10 campaign, Sneijder and Milito combined to help Inter secure one of the most famous trebles in European history. Sneijder's performances saw him win the Goal 50 - though he did controversially miss out on a Ballon d'Or nomination - while Milito scored 30 goals in all competitions, including the winner in the Coppa Italia final and both goals to beat Bayern Munich in the final of the Champions League.
N'Golo Kante (Leicester City & Chelsea)
An unknown when he arrived at the King Power Stadium, Kante was a force to be reckoned with in midfield as his ability to tackle and intercept almost at will formed the base around which Leicester's title win was built. He unsurprisingly earned a big money move off the back of that, only to take his performance level up a notch at Chelsea where he picked up a second consecutive Premier League winner's medal as well as both the PFA and Football Writer's Player of the Year awards.
Ronaldo (Barcelona)
Signed for a world record fee, Ronaldo proved to be a force of nature during his sole campaign at Camp Nou, scoring 47 goals in 49 matches across all competitions. His goalscoring exploits saw him become the youngest winner of the FIFA World Player of the Year award at the age of just 20.
Ruud van Nistelrooy (Manchester United)
Arriving from PSV for £19 million in the summer of 2001, Van Nistelrooy was tasked with scoring the goals as Sir Alex Ferguson looked to develop a new side after United's treble win two years earlier. Van Nistelrooy lived up to the hype, winning the PFA Player of the Year award having netted 36 goals in 49 matches across all competitions.
Luca Toni & Franck Ribery (Bayern Munich)
With Bayern reeling after finishing fourth in the 2006-07 Bundesliga season, Toni and Ribery were among the new faces brought in to freshen things up in Bavaria. Their impact was instant as Italy international Toni scored 39 goals and laid on 11 more in 46 games while Ribery was directly involved in 39 goals in the same number of games.
Zinedine Zidane (Real Madrid)
As Madrid embarked on the Galactico era, Zidane's full impact on the Blancos was not felt until the very last game of his debut season in 2001-02. Having previously netted on just 11 occasions in that campaign the France international volleyed in one of the greatest Champions League goals of all time to beat Bayer Leverkusen in the final at Hampden Park.
Robin van Persie (Manchester United)
With local rivals Manchester City having pipped United to the title the previous year, Van Persie was brought in from Arsenal to ensure the Red Devils had the firepower to win the title back. The Dutchman did just that, scoring 26 Premier League goals, including a hat-trick as the trophy was sealed with victory over Aston Villa at Old Trafford.
Sergio Busquets (Barcelona)
Having played under Pep Guardiola in the Barcelona B team, Busquets was promoted to the senior ranks at the same time as Guardiola took over at Camp Nou. Despite having Yaya Toure ahead of him in the pecking order, Busquets immediately established himself, earning himself a start in the Champions League final victory over Manchester United having earlier signed a new deal which included a release clause of €80 million.
Sergio Aguero (Manchester City)
Aguero scored 30 goals in his debut campaign at the Etihad Stadium having arrived from Atletico Madrid, but one of those strikes is remembered far more fondly than any of the others. With City being held by QPR on the final day of the season, Aguero popped up in stoppage time to fire in a late winner that sealed the title and snatched it away from Manchester United.