No doubt Manchester United's forward looks much better this season compared to last season's mess, but the defensive line still lacks that composure in defending goals from their opponent.
Amorim should rather change the 3-4-3 formation and think of a better formation that will suit the team and give a try; As we can all see, the premier League is a very competitive league which he might not succeed with the formation this season. I could recall clearly how Chelsea struggled during the season with Conte introducing this same strategy, and it was a hard one for them to win matches and stay top as one of the big team in the league.
Manchester United coach should see the basics when using 3-4-3 playing tactics, because there are other teams that have used this tactic and the results are less than optimal. Even though this tactic was used at Sporting CP and achieved success, it is not certain that in the Premier League it can be repeated, and in the defense area it will be difficult to withstand the fast movement and Amorin needs to adapt to change the direction of this.