Full-backs
2016: Nathaniel Clyne and Alberto Moreno
2018: Trent Alexander-Arnold and Andrew Robertson
In Basel, Liverpool were 1-0 ahead at half-time. Within 20 seconds of the second half, Alberto Moreno made an error which led to Sevilla's equaliser. He was at fault for the other goals as well, as the collapse led to a 3-1 defeat.
It looked likely that Moreno's Liverpool career was over. In contrast, Liverpool's current left-back is great going forward, defensively solid and has bags of energy. Andy Robertson was bought for £8 million- a real bargain buy. He seems to have solved the long-standing left-back problem at Anfield.
Nathaniel Clyne was possibly the Reds' most consistent player in 2015-16. He was very good defensively, while moderately fine in attack. He is still a Liverpool player, but he has been hampered by injury problems. 19-year-old Trent Alexander-Arnold has stepped up in his place.
He has shown some great promise throughout the season and possesses all the attributes to become a future Anfield legend. However, Clyne's consistency and discipline made him one of the key players of 2015-16. Alexander-Arnold still has a lot to learn, defensively in particular.
Verdict: Andrew Robertson and Nathaniel Clyne (2-1)
Center-backs
2016: Kolo Toure and Dejan Lovren
2018: Virgil van Dijk and Dejan Lovren
The £75 million signing of Virgil van Dijk is arguably one of the biggest Liverpool transfers in recent history. His calmness, strength and leadership qualities are what is required from a top-level defender. He has improved the Liverpool defence in a very big way. Kolo Toure also had the same qualities van Dijk has currently, except for quickness.
Toure was Liverpool's best player on the pitch in Basel, but it was evident that he couldn't be a regular in the Reds defence at his age. The Dutch defender has changed the entire dynamic of the Reds' backline with his presence. This is something Toure could have done in his prime, not when he is 35-years-old.
Virgil's arrival has brought an immense amount of improvement in Dejan Lovren's game. Lovren has been really inconsistent throughout his Liverpool career but after van Dijk joined, the two have formed a solid defensive partnership and helped Liverpool to keep 17 clean sheets in the league this season.
This is their highest total since 2009. Jurgen Klopp has done a fantastic job in improving the worst part of Liverpool's team, their defence.
Verdict: Virgil van Dijk and 2018 Dejan Lovren (4-1)