Murray has 'huge motivation' to still be in Britain's Davis Cup team
The former world number one is in a five-man team for this week's group stage in Manchester, along with Cameron Norrie, Dan Evans, Jack Draper and Neal Skupski.
Speaking after his recent disappointing second-round loss to Grigor Dimitrov at Flushing Meadows, the Scot said other players deserved a place in the team event ahead of him.
But the 36-year-old three-time Grand Slam champion, who has slipped to 41st in the world rankings, cut a more positive figure at a press conference at the AO Arena on Monday.
"At that moment, straight as I came off the court, I wasn't in a great place after losing in a Slam," he said.
"I said (to British team captain Leon Smith), if I'm not needed, I completely get that. But, for whatever reason, he asked me to come and I said I would come.
"I've always loved playing Davis Cup and any event where you're competing for your country. We have a great group of guys, I love being part of this team."
He added: "I do genuinely believe the team can win the event. That's huge motivation to be a part of it. I want to help the team in any way I can, whether that's on the court or off. We'll see what happens."
Britain have been drawn in a strong group with Australia, France and Switzerland and must finish in the top two to book their spot at the finals week in Malaga, southern Spain, in November.
It is eight years since Murray led Britain to the Davis Cup title virtually single-handed.
Britain have a stronger overall team now but that gives Smith selection difficulties and he faced criticism for choosing Murray and Joe Salisbury as his doubles pair when they crashed out at the same stage in Glasgow 12 months ago.
Salisbury won his third consecutive US Open title with American Rajeev Ram on Friday but did not make the squad, while the skipper must decide whether he will throw in 21-year-old Draper, fresh from his run to the fourth round in New York.
"I think we've got our best five here," said Smith. "Obviously we've got strength in depth, especially on the doubles side. In terms of selection for the matches, it's good. You want a strong squad, different options, because it is a long week."
Britain's biggest challenge is likely to come on Wednesday, when they take on last year's runners-up Australia, led by in-form world number 12 Alex de Minaur.
There are other groups based in Bologna, Split and Valencia, where Serbia and Spain will do battle, although a Wimbledon final rematch between Novak Djokovic and Carlos Alcaraz will no longer happen following the Spaniard's withdrawal.