You did ship four against Bournemouth, though, and squandered the game from a prime winning position. And in addition to that, it took until late November until you managed to both win a game and keep a clean sheet...that remains problematic for a side in contention for the title. All with a GK who's had his shaky moments and has come in for plenty of criticism.
Granted, you're nowhere near as leaky as the Rodgers side of 2013/14 was and you've really, really sorted out some of those defensive issues since the Bournemouth game with a few clean sheets since, but if you compare Liverpool to Chelsea they are on course for conceding under 30 goals, which will help them massively in their title challenge, especially since they're scoring more than enough as well.