The Hammers may have conceded 32 games in 18 games, the third worst record in the Premier League, but in their last four they’ve been breached just twice – and both goals were conceded against Pep Guardiola's runaway Premier League leaders.
It's been a dramatic turnaround, one that has included clean sheets against top of the current top six. So Moyes, despite there being opposition when he was appointed, is starting to win supporters over.
And just as the Scot has transformed the Hammers' defence, he has also worked wonders with summer signing Marko Arnautovic.
Before the former Everton manager's arrival, the Austrian had failed to score and was looking like one of the biggest transfer busts of the season.
But in the past fortnight, he has two goals in three games, including a winner against London rivals Chelsea and strike against his old club Stoke City. He has been revitalised.
There is little doubt Arnautovic has the raw tools to play out on the wing, but he needs space to drift inside and linked with a No.9.
Looking at his touch map from the games against Everton, Brighton and West Brom, you see a player forced to try to influence the game from out on the flank instead of more centrally.
In the defeat against Watford, you can see from the graphic below, via WhoScored, that apart from his four shots, all of his possession came from the right-hand side.
Fast forward to the Hammers' last three fixtures and Moyes has changed things up.
Playing 3-4-3 and using Arthur Masuaku as a wing-back and Aaron Cresswell as a centre-back, space in the attacking third has opened up. And without Chicharito or Carroll from the start, Arnautovic has been leading the line.
Against Chelsea, he many have only managed 23 touches, but they were much better spread out. And one was decisive.
Receiving the ball with his back to goal, Arnautovic waits, plays a lovely one-two with Lanzini, before curling his effort beyond Thibaut Courtois.
Arnautovic is a rare forward. He’s big and powerful, capable of holding off defenders, but has a neat and intelligent touch. He can beat defenders off a dribble, where he combines his speed and strength to great effect.
He’s growing into the new role under Moyes, with 45 touches against Arsenal and 36 in the win over Stoke.
All six of his shots at the Bet365 stadium came inside the box and you can see from the graphic below he was much more mobile and able to get himself involved in West Ham attacks.
Arnautovic finished with an Expected Goals (xG) score of 0.80 – his highest of the season. xG is a model which applies a value to every shot taken based on the likelihood of it being scored and the quality of the chance.
He now has an xG rating of 2.56 for the season, and with two goals to his name he is just under his target.
No doubt the potential for more is there, and it shows how unproductive he was when 53 per cent of his total (1.38) has come in the last three games.
If he continues on this path for the 20 games that remain, he could surpass last year’s total and finish with an xG of around 12 – which is close to what he managed in 2015/16 when he scored 11 times.
However, Arnautovic could easily surpass that return of goals and assists under Moyes, especially with the talent he has around him.
“Every day we have to work hard under this coach and there are no excuses,” said Arnautovic. “Everybody needs to do his main job and do two or three more jobs on the pitch.
“We are working hard as a team and I think you could see that in the game and if we continue to do that, we will be hard to beat.”
Discipline seems to be at the forefront of what the former Manchester United boss has changed, but moving Arnautovic into a position where he can use his physicality and ability on the ball has made the world of difference.
It’s one thing to be a winger who can drift inside and cause danger, but when you park them on the flank and don’t give them the freedom to roam the final third, you are clipping their wings.
Once his confidence is back fully, expect the Austrian to continue to soar.