When head coach Patrick Vieira took over New York City FC last year, he made it clear he wasn’t afraid to shuffle formations or players — even when everything was working just fine.

That mentality carried over into this season and into last week’s 2-1 loss at DC United, when Vieira changed a successful formation (4-3-3) to a nonconventional configuration (3-2-2-3) with little to show for it. Vieira thought the change would surprise DC United, but it proved entirely counterproductive, especially considering NYCFC had embarrassed DC United, 4-0, at Yankee Stadium just a month prior using the 4-3-3 formation.

“The system you choose will allow you to control the game a little bit more,” Vieira said as NYCFC (2-1-2, seven points) prepared to hit the road to face the winless Philadelphia Union on Friday night (7 p.m., ESPN). “But we need more than the system to win football matches. If we don’t do it, we’ll struggle.”

NYCFC’s tactical shift against DC United meant winger Jack Harrison was forced to track back on the defensive end, which slowed the team’s attack. Vieira said he prefers Harrison to play further up the field, though he applauded the 20-year-old’s commitment to defending. And he said he would like to see his defenders remain in position further up the field, so wingers aren’t forced to come back.

“To allow [wingers] to get a bit more higher, we need Fred [Brillant] and Alex [Callens] to get a bit more wider,” Vieira said. “It’s not just about one piece, but when you move one or two pieces, it will change the shape of the team.”

Vieira said he opted to start Brillant for the first time this season because he fit better in the new alignment’s three-man defense, but Brillant’s nonchalant giveaway resulted in an easy goal for DC United. It seems likely Vieira on Friday will revert to the 4-3-3 formation — and the normal four-man backline of Ronald Matarrita, Maxime Chanot, Callens and Ethan White — to get a result, as when NYCFC beat the Union, 3-2, at home last June.

That system allows NYCFC to possess much of the play. To Vieira, though, possession is not enough.

“We need to add something more to our game to be more competitive,” Vieira said. “We are giving a lot of hope to the opposition and if we don’t change our mindset, you’ll beat us.”

NYCFC couldn’t have an easier assignment than against struggling Philadelphia (0-2-3, two points), which has scored just five goals while allowing nine — tied for most in the Eastern Conference.