There's been a feeling - probably because he played in midfield last year - that Daley Blind is a stop-gap at the back for United.
But, in the last two games against City and Everton he's started to show that he might be a long-term solution.
He won't face tougher tests than Sergio Aguero and Romelu Lukaku but he stood up and handled both well.
Credit where it's due, Louis van Gaal turned the game and turned one point into three with his substitutions against Everton.
He's taken a lot of stick for his habit of swapping full-backs, but he was quick to take off the struggling Marcos Rojo and bring on Timothy Fosu-Mensah at the interval.
When the visitors were threatening to overrun United in midfield, Ander Herrera replaced Michael Carrick.
Fosu-Mensah played a key part in the decisive goal and Herrera brought calm and composure to steer United back on track.
Rojo was taken off early against City and he was lucky to last until half-time in this one.
He never got to grips with Gerard Deulofeu and it was no surprise when Fosu-Mensah came on for the second half.
With Luke Shaw absent for most of the season and Blind slotting in at centre-back, this was a chance for Rojo to make himself a regular- even when Shaw is fully fit.
But, as it stands, the England full-back cannot return soon enough.
Rojo has failed to convince across his two seasons at the club and must now be walking a tightrope in terms of his long term future.
Fosu-Mensah was brought on at half-time and looked fantastic.
It was his intelligent run and cross that gave Anthony Martial the chance to score the winner.
The Academy graduate looks a real prospect and, crucially for Louis van Gaal, has proved to be versatile.
Already in his short first-team career, the Dutchman has played at left-back, right-back and centre-back- and he's a central midfielder by trade.
The squad has been thinned out to such an extent that United don't have too many attacking options but there was still no place on the bench for either Adnan Januzaj or Andreas Pereira.
Both of their careers are in danger of stagnating and they need games.