Man United don't need an additional winger because they already have potential young players. This was no longer a matter of Ronaldo or the winger.
Their wingers don't play too well. Jadon Sancho is simply a very disappointed case. He has never reached to his performance level as he did in Dortmund. Rashford is used at winger and striker and I don't think Rashford plays too good at these positions. Ganarcho is a new discovery from Ten Hag but a few impressive matches are not enough to put all pressure on the young player.
At the moment Erik Ten Hag is always trying to experiment with every line and it is clear that the 2 goals in the first half against Aston Villa were errors by the Benfica defender. He was too focused on guarding the transfer players who had been prepared by Unai Emery and moreover Lindelof was always unable to compete to secure the ball. So that makes Martinez have to cover up his mistakes at the back.
As a new coach in a new club, you have to try some formations to find a best one for players you have. Ten Hag is just doing that job and the temporary result is acceptable that allows him to continue his trials.
The defeat against Aston Villa confirms a fact that Manchester United need to have some supplements from transfer market. If they want to finish in top four and aim at higher targets next season, they should start a good preparation since this season.