Frenkie de Jong scored the only goal of the game as the Catalans moved to within ten points of LaLiga Santander leaders Atletico Madrid.
"This month is very important for our aspirations because we have lots of games away from home and, if we win them, I think we can fight," Koeman said on Barcelona's title chances.
"We've seen this weekend that it's not easy to win away from home. If a team [above us] goes on a bad run, the gap can be closed, but it depends on us winning."
There were a few eyebrows raised when Antoine Griezmann was left out of the starting 11 against Huesca. The Frenchman didn't come on until the 80th minute, as Martin Braithwaite and Ousmane Dembele played instead.
"I trust every player in our squad, but if we choose to have three central midfielders, there's room for three forwards," Koeman explained.
"With Leo, we went for someone who gets in behind more like Dembele and we have to choose between Martin or Antoine up front.
"Martin did well. He's the No.9 we need in these types of games but leaving Griezmann on the bench means nothing. We have lots of games and we need every player.
"[Dembele] is a player we need because we're missing Ansu Fati, who is also a striker who can play out wide. He gets in behind the opposition, he's good one-on-one...
"It's always important to have one who gets in behind to take advantage of the quality of Leo and the midfielders."