My analysis of the team as it stands is that the single most functional part of it, is the defence. From an engineering standpoint as such, how it operates is still within the tolerances it needs to withstand for its purpose of achieving a successful Premier League and European campaign season.
However, what is not in dispute is that it's functionality becomes significantly degraded upon any of the components within the mechanism succumbing to fatigue and fracturing under stress to cause almost irreparable damage (Tierney, Tomiyasu and Partey).
Remedial action by the engineer in now recasting those components out of titanium instead of aluminium, or alternatively improving the design to now include a type of actuator suppressing any harmful effects are good solutions in solving the problem.
That we are currently unable to enter the realm of Sci-Fi technology to enact our own version of the Six Million Dollar Man and utilise bionic legs for Tierney, *Partey and Tomiyasu is an extreme hindrance to the first option as is their replacement with replica players impervious to injury.
Therefore, the recruitment of Lisandro Martinez or a very similar player would equate to being that actuator as the second and more feasible option, with the design improvement now moving the Ghanaian into central midfield as the perpetual motion box-to-box midfielder, whilst situating the Argentine behind him in the defensive midfield slot to best utilise his mixture of assassin and quarter-back like qualities.
In the event of Tierney once again imitating a KitKat and activating Martinez's need to nullify his loss, Partey would effortlessly slide back to accommodate that or offer the option of a slight modification to operate in tandem with Elneny now as the deepest midfielder.
*Also scheduled to have a bionic eye fitted in addressing the inaccuracy of his long range shooting.