Increasingly in modern football, it feels as if you have to buy players not just based on their talent, but also on their attitude.
How many times have we seen in recent seasons a player upset the applecart at a club and force through a move away through sheer disruption?
And West Ham are, of course, no stranger to this issue.
The Hammers confirmed his arrival earlier in the day, and the Frenchman backed up the announcement with some pretty impressive words.
Speaking to the Hammers’ official website, he said: “For me I can guarantee that I will give 100% for the club, because the club has given me this confidence and I will try to give it back every day in every game.
“I will always give 100% and respect the club. I think this is a normal thing and that I can guarantee.
“I know it’s a big transfer and there is a lot of expectation around me, and I just want to make people proud of this transfer and I will give everything I have.”
Chances are Haller couldn’t care less about the Arnautovic saga that has preceded his arrival, and it is more than likely that his comments are merely coincidental, media-trained speak, but for a fanbase that has been through the wringer with big money signings, and who have had to put up with their star man treating the club like dirt before disappearing into the night, the striker’s words will no doubt come as a a hugely reassuring thing.
The Hammers will no doubt love Haller even more after hearing this.