Manchester United defender Lisandro Martinez said "anger and frustration" at defeat to Atletico Madrid led to his swipe at the club's board for a lack of investment in the transfer market.
The English giants lost 2-0 in Spain on Tuesday in the Champions League. They are also off to their worst start to a Premier League season for 40 years.
Martinez took aim at technical director Jason Wilcox, saying he "100 percent" expected more investment in the squad during the transfer window after United finished third in the Premier League last season to return to Europe's top competition.
United signed three midfielders - Carlos Baleba, Youri Tielemans and Andrey Santos - for around £150 million ($198 million), but their spending fell far short of some of their Premier League rivals.
"After the match, I spoke out of anger and frustration at not getting the result we all wanted," Martinez posted on social media.
The Argentine international's comments were backed by some fans, but Martinez has been criticised for his own part in United's poor start to the season.
He scored an own goal in a 1-1 draw at bottom-of-the-table Fulham last month and was outmuscled by Dominic Solanke as 10-man Tottenham salvaged a point at Old Trafford last weekend.
"When I talk about wanting more, I'm talking about the ambition we must all have as part of this club. To keep growing, to become stronger and to have everything we need to compete at the highest level.
"These are standards we must all hold ourselves to, starting with me.
"I believe in my team-mates, our manager and everyone working to help this club move forward. I'm convinced that the way forward is to keep working together, with ambition and commitment."
The pressure is rising on United boss Michael Carrick just months after he was handed the job on a permanent basis.
Carrick's men travel to historic rivals Leeds on Sunday before another Champions League trip, to Italian side Como, on Wednesday.