West Ham United are two games from Wembley if they win at Old Trafford.
The Irons return to Old Trafford for an EFL Cup quarter-final clash tomorrow night after earning a 1-1 draw away to Jose Mourinho's side at the weekend.
Diafra Sakho's opener inside two minutes was cancelled out by Zlatan Ibrahimovic in a contest which saw home boss Mourinho sent to the stands in the first half.
That stalemate saw the Red Devils slip 11 points behind top-of-the-table Chelsea and there seems to be a bit of pressure on the Portuguese to start picking up results.
Mourinho has already won the League Cup on three occasions across two different spells with Chelsea, and Mariner believe his love affair with this competition will continue against West Ham.
He told ESPN: "I think he [Mourinho] is going to love it [League Cup] even more because he needs a victory - especially at Old Trafford.
"He's under the microscope after what happened at the weekend, getting sent off. I think he'll field a fairly strong side. He needs the win. I'm going for Man United."
Slaven Bilic's side have been poor for the most part this season and, with the visit of Arsenal looming large on Saturday, the Croat may elect to rest some of his bigger names - especially given his ever-extending injury list.
West Ham are 16th in the Premier League table after 13 matches, one point above the drop zone. The league must take priority over the League Cup for Bilic.