Jurgen Klopp has spent over £150m in recent months as he looks to finally end his Liverpool silverware drought.
The Reds have signed Naby Keita, Fabinho, Alisson and Xherdan Shaqiri this summer.
And die-hard Everton fan Barton admits the club’s business has got the blue half of Merseyside worried ahead of the return of the Premier League.
“When we look across Stanley Park, no matter what any of us say, and see the big German [Jurgen Klopp], the style they’re playing, and the way they have invested again – it’s nervous times for Evertonians,” he told talkSPORT.
“I honestly think they could get really close to their first title in 20-odd years.
“It will be really close.”
Liverpool are by far the biggest spenders in the Premier League this summer.
And Klopp’s decision to splash out on new arrivals has made other managers stand up and take notice.
Speaking last week, Manchester United boss Jose Mourinho said: “The problem is you have to invest well and, honestly, I think they did very well because every player they bought are quality players and I’m happy for them.
“And I’m also happy to smile and to see that you can change your opinion and change as a person, is funny [meaning Klopp].
“That’s OK. But maybe this season finally you demand they win.
“Now you have to demand and say the team – with the investments you are making last season and you make now, that will probably be the record of the Premier League this season, a team that was a finalist in the Champions League – you have to say you are a big candidate, you have to win.”