A lot is resting on Arnautovic, a club record £24m buy from Stoke, for both West Ham and the Austria forward.
"You can see in the summer transfer window that they spend very well, with good players because we want to achieve a lot of stuff and be better than last season".
"I've had three fantastic years playing in Spain and Germany, but England was really the first big chapter in my career and I am so happy to be back".
"Of course to be back to Old Trafford and to start this adventure this season with my new team, it's going to be a very important [match]".
Do West Ham have a long term plan & philosophy? As a starter in his first season at Leverkusen, he had 26 goals.
The Ghana global demonstrated his class in patches for the East Londoners last term, but it wasn't a triumphant maiden campaign in the capital by any stretch of the imagination.
The 29-year-old scored 26 goals across all competitions in his debut campaign and followed it up with a respectable 12 in an injury-hit 2016-17. This time past year, the first cracks began appearing in the rocky relationship between player and club. Unfortunately, much of his football at Old Trafford came from off the substitute's bench and eventually he became exhausted of playing a supporting role and joined Bayer Leverkusen.
If manager Slaven Bilic opts to use a 4-4-2 system with Carroll and Hernandez leading the line, the Hammers could find themselves forcing their way into the top six of the Premier League; qualifying for the Europa League.
"He is the guy that naturally the ball comes here, rebound here, rebounds there, boom - goal". We made decision with the manager to buy players proven in Premier League.
The Austrian is predominantly a left winger and offers a creative outlet out wide too, different to that provided by Michail Antonio on the right flank.
And that optimism is a far cry from this time last season, when most of their signings sank without trace.