Three days ago the Catalan club's sporting director Andoni Zubizarreta said he thought David Moyes' side's pursuit of the midfielder was over, after they had two bids turned down.
Zubizarreta's prediction would appear to be vindicated in light of reports that United have turned their attention to signing Marouane Fellaini from Everton instead.
Fabregas started in Barcelona's 7-1 win over Thailand on Wednesday and after the game Martino insisted he was not concerned about the player's future, concerning himself more with the fitness of club captain Carles Puyol, who is still recovering from a knee operation.
"Fabregas is still our player and he will be with us for this season," the Argentinean coach is quoted as telling AS.
"Right now I'm more worried about whether Puyol will recover."
The declining physical state of the 35-year-old Catalan defender has made buying a centre-back one of Barcelona's priorities this summer.
However, with 10 days to go until the new season starts, the Primera Division champions have only made one signing - Brazil forward Neymar.
The club have now reportedly made a £35 million bid for Chelsea centre-back David Luiz, but Martino refused to shed any light on a possible move for the Brazilian.
"I'm in Thailand, I know nothing about any negotiations," he said.
Neymar opened his account for Barcelona by netting the game's first goal after 12 minutes, with Lionel Messi doubling the scoreline a minute later with a penalty.
Martino was encouraged by how the two forwards played on the first occasion they had started together for the Catalans.
He said: "They combined well and played in different areas of the pitch. The connection between Neymar and Leo was the most interesting thing about the game and they played as well as we expected.
"They combined well and scored goals, but they also combined with other players, which is what you expect at this level."
Pedro scored Barcelona's third and fifth goals, while Messi hit the fourth to complete his own brace.
Teerasil Dangda pulled one back for the hosts before half-time from the spot, before Pedro completed his hat-trick and Alexis Sanchez scored a seventh.