Enzo Maresca's naive tactics were exposed and his side made too many mistakes playing out the back - but there was ONE positive for Chelsea: FIVE THINGS we learned after the Blues' humiliating 4-1 defeat by Celtic

Chelsea were humbled by Celtic in Indiana on Saturday as Enzo Maresca's side fell to a 4-1 friendly defeat at Notre Dame Stadium.

Matt O'Riley, Kyogo Furuhashi, Luis Palma and Michael Johnston found the net for the Hoops before a late Christopher Nkunku penalty kick got the Blues on the scoresheet.

This was Maresca's second pre-season outing as Chelsea's new manager and his tactics were humbled by the Scottish side.

His first game in charge was a 2-2 draw against Wrexham earlier in the week. 

Mail Sport's Kieran Gill was at Saturday's game and jotted down five things we learned from the action.

Naive Chelsea played like Big Ange's Spurs

The number of times that Celtic beat Chelsea's high line with a single ball in behind was concerning, made worse by the lack of press from Enzo Maresca's players which gave their opponents plenty of time to pick a pass.

That was precisely how Celtic made it 4-0, and it made you think of Tottenham under Ange Postecoglou last season. Premier League opponents will try to expose Chelsea's high line over the upcoming campaign because all it requires is the right ball and run to open them up.

Chelsea's right-hand side was particularly vulnerable when Reece James was inverting into midfield as it left a giant gap. Maresca has work to do in the defensive department because throughout this match, his players looked like mannequins. Though this is only pre-season, conceding four goals is embarrassing for Chelsea in any game.

Nkunku looked lively and played the full 90 

One positive for Chelsea is the sharpness of Christopher Nkunku, who was their liveliest attacker in an otherwise lacklustre first half. 

After missing most of last season through injury, the 26-year-old Frenchman carried a threat across the front line and was the only player to complete the full 90 minutes.

Marc Guiu was impressive also, occasionally being forced to the ground by Celtic's defenders and yet finding a way to keep hold of the ball. Though he is only 18, the Spaniard is showing he could handle the physicality of the Premier League.

If he stays, that is, because Maresca wanted to see him in pre-season before deciding whether to send him on loan.

Nicolas Jackson still has not trained with the first team in the United States so Guiu is getting his chance to impress Maresca, and I'd say he's taking it.

Schmeichel's still got it

Kasper Schmeichel has still got it. The 37-year-old, who joined Celtic on a free transfer, was denying whatever came his way.

Back-to-back saves to deny Nkunku and then Carney Chukwuemeka were the best of the bunch.

Speaking of Denmark goalkeepers, Chelsea are on the verge of signing Villarreal's Filip Jorgensen for £20.7m on a seven-year contract.

He will act as competition for Robert Sanchez with Djordje Petrovic, not currently on the United States tour because of an injury, potentially being sold.

Sanchez made one sensational save here but looks shaky whenever trying to play out from the back, often looking long instead.

Chelsea likely won't play on a pitch this bad all season 

Mail Sport received confirmation on Saturday that Cole Palmer, Conor Gallagher and Marc Cucurella will not join Chelsea's squad in the United States, but that isn't the worst news as it keeps them away from these pitches.

There were officials testing the bounce of the ball at Notre Dame Stadium and let's just say it wasn't the liveliest.

The playing surface here did not help the pass, pass, pass style of play that Maresca is trying to implement as the ball was constantly stalling.

But that is no excuse for being embarrassed by Celtic.

Mistakes par for the course 

When Pep Guardiola took over Manchester City and ordered his team to play out from the back, they made mistakes.

The same will happen with Chelsea over the next season. Already we have seen a howler in pre-season because Benoit Badiashile gifted away the ball to Celtic so that they could score.

Chelsea supporters best get used to having hearts in mouths at Stamford Bridge.