The Swede says management failed to prepare for this season, with the team now sitting in 16th place on the Premier League table.
"(The top clubs have) been doing it many years," rapped Kulusevski after defeat to Nottingham Forest on Monday night.
"They know exactly what they're doing. They're bringing in a lot of players that are ready to play both competitions. And they are prepared for it.
"This year we cannot say that we're prepared for it because we had so many injuries and we did a lot of things wrong from the beginning of the season and we're paying for it right now. After big nights like Thursday, you always go down. That's why teams who are in more competitions are paying (a price).
"We're not handling it right, we're not handling it well. Because after 16 minutes we'd conceded three goals, with the offside goal. Then it's hard to win football games. It's not good enough. Then we played some good football but if you're not doing everything right, you will not win games."