Joel Ward is right, Chelsea have one frailty stopping them becoming 'real title contenders'
Joao Pedro's second-half goal saw the home side earn a point, after the visitors had come from behind to take the lead.
Morgan Rogers continued his excellent form by finding the bottom corner in just the seventh minute, making it three goals in just four Premier League games this season.
But a quickfire brace from Mohamed Belloumi saw Hull take a shock lead and leave Stamford Bridge stunned into silence.
The Blues came back in the second half and pushed for a winner, but ultimately came up short to mark a second consecutive Premier League game without victory.
Hull remain unbeaten in their opening four league games, and are quickly becoming one of the stories of the season.
Joel Ward spells out Chelsea needs
Chelsea have been tipped by many to potentially become Arsenal's closest challengers for the Premier League title this season.
The Blues are clearly an incredibly exciting team to watch, with Morgan Rogers, Joao Pedro and Cole Palmer forming a huly potent front three.
But Alonso's team have kept a clean sheet just once across all competitions this season so far, and have conceded at will in the Premier League.
The ease in which Hull turned around Saturday's contest showed a serious lack of solidity, and an indication that more problems could arise later in the season.
Arsenal on the other hand, have conceded just once in five games so far this season and appear to be the very definition of solidity.
Speaking to BBC 5 live, Joel Ward said: "To be real title contenders, you have to have a foundation and you have to be solid in your structure. You can't be conceding two or more goals in every game.
"It makes it so difficult and it's not good enough. They need to make it harder for teams to score against them.
"You rely on your front three to score goals and create for the team, but there's going to be games where that doesn't happen and it's not flowing, so you need to make sure that you've got the structure and strength at the back to stop teams from creating opportunities."
Chelsea still look inexperienced
Much of Chelsea's summer business looked to be about adding experience to a very young squad.
The likes of Danny Welbeck and Jordan Henderson arrived, and were followed by players like Emi Martinez, Pep Chavarria and Maxence Lacroix.
Yet there is still a distinct feeling of inexperience in Chelsea's play. Saturday's game was yet another example of the work that needs to be done at Stamford Bridge.
If the Blues are to challenge for the Premier League title, they may still need to add something more.