That is according to eight-time Olympic Gold medalist and huge Manchester United fan Usain Bolt.
United are back in the Champions League after a year away following their Europa League final victory over Ajax in May.
Manager Jose Mourinho has strengthened his squad by the additions of Romelu Lukaku, Nemanja Matic and Victor Lindelof, as well as the return of Zlatan Ibrahimovic, in a near £150million spending spree.
However, Bolt reckons more potency up front and solidarity at the back is needed when the transfer window reopens in January.
“The Champions League is going to be hard, you know what I mean,” Usain Bolt told ESPN.
“I think we’re missing a few vital (players), I think we need maybe one more striker, maybe a stronger defence and then we will be fine. One striker, one defender.”
Bolt is excited by Zlatan Ibrahimovic coming back though but expects the Swede to take time to regain fitness.
Ibrahimovic has been out since April due to a knee injury he picked up in the Europa League quarter-final win over Anderlecht.
“For sure Zlatan will be good but because he’s starting so late, because I think they said he’s not going to start playing until January, he’s not going to be in shape,” Bolt added.
“It takes time to get into playing football, so it’s going to be tricky.
“The teams looks good but anything is possible, right?”
Manchester United have won their opening three games of the Premier League season and sit top of the table.