Liverpool had an offer accepted by Real Sociedad for Zubimendi, who ultimately chose to remain in San Sebastian this season.
Asked if Zubimendi's decision inspired the Gravenberch switch, Slot said: "It is not that much of one holding midfielder, it is a bit more two - and one of those two can be a bit more attacking," said the Liverpool boss. "I think the player you mentioned could have fitted in in one of those two roles and Ryan can fit in both roles like Curtis (Jones) can, Alexis (Mac Allister) can and Wataru (Endo) can.
"If I could have bought him (Zubimendi) then maybe I could have rotated a bit more and you guys (the media) would be a lot more happy about it! But there is no point talking about Zubimendi any more because he stayed with Real Sociedad and we've moved on and we are really happy with Ryan.
"But a club like ours should always try to bring in good players who can help the team to win because it is going to be a long season and therefore you need a lot of good players.
"That has been proven in the Premier League if you look at the ones who have won the league in recent years. They have had a very big squad. So I don't think it would have affected Ryan's playing time."