The midfielder was speaking after featuring in United's 5-2 friendly triumph over LA Galaxy, having been questioned over a possible return to LaLiga.
Ernesto Valverde's appointment at Camp Nou led to speculation Herrera may reunite with his former Athletic Bilbao coach, but the 27-year-old dismissed the idea.
"There is nothing certain about Barcelona because I am very happy at United and I feel valued and focused here," said Herrera, who has one year left on his contract.
His denial comes after one British newspaper claimed the Spaniard was on the brink of agreeing terms on a four-year deal worth £41.6million ($70M).
The Daily Star Sunday reported that United were ready to make to make Herrera one of their highest-paid players, with the news set to be confirmed during their tour of America.
Herrera also expressed his disappointment at seeing a move for compatriot Alvaro Morata fall through.
"Of course I wanted to have Morata as a team-mate, he was very close because the two clubs negotiated," he continued.
"Too bad he is not with us, but I wish him well."