Trent Alexander-arnold(premium option)
Alexander-Arnold epitomises the position of a full-back in the modern game with his high offensive output. He has 14 assists and 2 goals so far this season. But his high defensive work-rate has also contributed to Liverpools sturdy back-line. With his 1.59 tackles/game and 6.46 recoveries/game to go along with his 2.65 attempted assists/game he is undoubtedly the premier defensive option in the game.

But along with his high output comes a heft price tag of 7.8 million. But a big price also brings the guarantee of a starting berth, Alexander-Arnold has started 97% of Liverpools games in the Premier League this season. Along with Liverpools lack of depth at RB, it makes him virtually immune to rotation, and a must-have for the remainder of the season.
matt doherty(premium option)
Doherty is another one of Wolves star-players from last season, contributing to 4 goals and 7 assists along with 8 cleansheets in the 18/19 campaign. But he had a slow start to the season sometimes even finding himself on the bench for certain games. For the first 23 gameweeks he only contributed to 1 goal and 1 assist. But since Wolves shifted back to a 3-4-3, which sees Doherty pushed up to a right wing-back role, he seemed to have rediscovered his form.

Since the positional change, his numbers have gone up in nearly every offensive statistical category. His shots on target have gone up from 0.56/game to 0.73/game and his attempted assists/game have also increased from 0.45 to 0.60. With Wolverhampton boasting a solid defence and no commitments to European Competitions, Doherty is a premium differentiatial option owned by only 8.8% of FPL managers.
Aaron wan-bissaka(mid-range option)
Wan-Bissaka was one of the breakout stars of the 18/19 campaign for palace. His superior tackling and interception rate made him a candidate for earning multiple BPS(bonus points) every time Crystal Palace kept a cleansheet. He has certainly maintained his defensive output with Manchester United this season contributing with 3.90 tackles/game, 2.0 interceptions/game and a massive 5.64 recoveries/game.

At 5.3 million Wan-Bissaka is a great option, especially in a United team who is massively underperforming their Exp CS(expected cleansheet) of 10.49, amassing only 7 cleansheets. With a favourable run of fixtures coming up Wan-Bissaka is a great option to consider at his price.
John Lundstram(budget option)
Lundstram has already written himself into FPL-folklore, with his early season exploits as 4.0 out of position defender. Despite being classed as a defender in the game, Lundstram’s position is much further forward at CAM. He has already contributed 4 goals and 4 assists this season, and with him being classed as defender he gets an extra 1 point for goals and assists along with the added 4 cleansheet points.

But even at his current price of 4.9 he is an option to consider. His replacement, January signing Muhamed Besic has struggled to find his feet in the League, which saw Lundstram regaining his regular starting position just before the season hiatus.
ALL STATS FROM FANTASYFOOTBALLFIX.COM