Ibrahimovic retired from international duty following Euro 2016, but made it clear he would be open to returning after his country secured a place in Russia.
However, Sweden boss Janne Anderson refused to budge on that basis, instead preferring to give a chance to the players that helped Sweden qualify.
That faith appeared to have been well-placed as the Swedes got off to a winning start, beating South Korea 1-0, but nevertheless, Forsberg believes they would be better off with the LA Galaxy man.
"We made it to the World Cup without Ibrahimovic. But it's a fact: Sweden would be better with Zlatan," he told German publication 'Bild'
"But he's not with us now and it should no longer be an issue. We are strong as a team, always bring in our mentality and passion."
The RB Leipzig playmaker is not alone in his assessment, with Germany's Timo Werner in agreement with his club team-mate.
"I can understand Emil — Zlatan Ibrahimovic is an outstanding footballer who can make a difference," he added.
"Another star would have been good for the World Cup. That's why it's a bit of a shame. But Sweden is strong enough."