Despite attempting 20 shots at goal against Huesca in La Liga on Sunday, Barcelona could only come away with a 1-0 win over the division’s bottom club.
Frenkie de Jong’s 27th minute goal from Lionel Messi’s brilliant pass was all the Blaugrana needed to claim their eighth victory in 16 La Liga games this season.
Barcelona failed to replace Luis Suarez after the Uruguayan joined Atletico Madrid in the summer, leaving Antoine Griezmann and Martin Braithwaite as Koeman’s central attacking options.
Griezmann has scored three goals in 15 La Liga games this season while Braithwaite has two goals from 13 outings.
The Dutchman believes additional firepower in attack will help Barcelona achieve their aims this season.
"I trust each player in our squad," Koeman told reporters. "But if we choose to have three midfielders there is room for three forwards.
"With Leo we bet on someone with great depth like Dembele, and we have to choose between Martin or Antoine at the top and Martin has done it.
"It's a nine that we're missing in these games but it doesn't mean anything in regards to Antoine's substitution. We have a lot of games and we need all the players.
"We have said several times, at the beginning of the season, that we need someone at the top to have more competition and more goals, more effectiveness, but this depends on many things."
Barcelona, who face Paris Saint Germain in the Champions League next month, are fifth on the table, 10 points behind leaders Atletico Madrid.
