Keown believes Lukaku was bought in to be Mourinho's new Didier Drogba, but questioned whether he had the consistency to hit the same heights as the Ivorian forward.
You could easily say that any one of six teams (or who knows, maybe more) could win the title this year, and I don't know if there are any other leagues around the world, never-mind among the major leagues, where we could say that.
Romelu Lukaku, Victor Lindelof and Nemanja Matic have so far arrived this summer, but Mourinho always meant to make four acquisitions. The 20-time English champions are being tipped for the title alongside Manchester City, after a summer of wise spending, and against The Hammers on Sunday, United should expect to win as we were unbeaten against the East Londoners last term.
Mourinho has seemed adamant at improving the squad's league position this time around and it appears like the message has been well received by his players.
The Swedish striker was released by United at the end of last season after he suffered a serious knee injury back in April in the Europa League quarter final tie against Anderlecht.
"We have added three players, one defender, one midfielder and one attacking player", the Portuguese boss explained.
Marcos Rojo, Luke Shaw and Ashley Young are injured. Our levels of confidence and knowledge are higher so I am happy to start the season.
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"I thought United's signings were particularly good with Romelu Lukaku at the top of the pitch, Nemanja Matic in that midfield role and Lindelof at the back", he told Sky Sports.
'I was thinking, three transfer windows, I need that.
"We always had more goals with wingers, midfielders getting 10 goals, central defenders getting five goals and last season that did not happen much".
When we look at the rest of the table, you could once again make a case for saying that any of the remaining sides could be in the relegation fight.
I understand by doing 75 percent of what I asked, the club did very well.
"I will just go with everything I have to try to win every match we play".
"It's the way I trust the player is going to perform, so I think it was a fantastic signing for us".