Chelsea head coach Enzo Maresca said his players were still trying to adjust to his playing style after losing 4-1 to Celtic in a pre-season friendly in Indiana on Saturday.
Christopher Nkunku's 89th-minute penalty was the only consolation for the Premier League side, while goals from Matt O'Riley, Kyogo, Luis Palmer - following a Benoit Badiashile mistake - and Mickey Johnston provided Brendan Rodgers with a much happier afternoon.
"Off the ball we need to improve things," Maresca said, after also having to defend his "risky style" following a 2-2 draw with Wrexham last Thursday - his first game in charge.
"You can see sometimes we confuse when we need to play short and when we need to play a little bit longer but that is part of the process.
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"We maintained a high line but when the ball is not under pressure, you need to drop. We are still confusing some things on the ball and off the ball. It is normal in this moment when we are trying to do something new."
Chelsea had 23 shots to Celtic's 14 and almost two-thirds of the possession, but were again guilty of some sloppy defending, leading to O'Riley's opener from a short corner, before two goals in the space of three second-half minutes sealed their fate.
Some carelessness from Badiashile presented Palma with Celtic's third and then a simple ball over the top released Johnston, who made it 4-0. Nkunku scored from the spot late on following a foul on Raheem Sterling.
Despite two lacklustre results, Maresca finished by insisting his team would be ready for their Premier League opener against champions Manchester City on August 18, live on Sky Sports.
He can only hope for better when meeting Mexican side Club America in Atlanta on Wednesday.
Chelsea's remaining pre-season schedule
July 25: Chelsea 2-2 Wrexham
July 27: Chelsea 1-4 Celtic
August 1: Chelsea vs Club America - Mercedes-Benz Stadium, Atlanta, kick-off 12am
August 3: Chelsea vs Man City - Ohio Stadium, Columbus, kick-off 10.30pm
August 7: Chelsea vs Real Madrid - Bank of America Stadium, Charlotte, kick-off 12am
August 11: Chelsea vs Inter Milan - Stamford Bridge, kick-off 3pm
Rodgers delighted with preparation for new season
Brendan Rodgers declared Celtic's pre-season tour of the United States had been the perfect preparation for his side's title defence.
The Scottish champions followed up wins over DC United and Manchester City with another four-goal showing in Notre Dame Stadium in Indiana, the home of the Fighting Irish American football team.
A late penalty deprived Celtic of a clean sheet but that took little away from Rodgers' feeling of satisfaction as his side gear up for next Sunday's William Hill Premiership opener at home to Kilmarnock.
"We still have another good week's work before we arrive into there but this preparation phase over the last 12 days has gone as well as it possibly could have done," he told Celtic TV.
"Players looking sharp, looking fit, looking intense, and then the quality of the football to score the goals. We have scored 12 goals in three games and two of those against really high-quality opponents.
"So we are in a really good place. Now, get back safely and prepare for flag day."
Despite losing loan players Adam Idah and Paulo Bernardo and not adding any outfield players to their squad other than getting Johnston back from West Brom, Celtic have carried on from where they left off at the end of last season, when they won 11 of their last 12 games to clinch the double.
Rodgers was delighted with the intensity his side brought to the friendly matches.
"I know that big teams don't want to lose games whether it's pre-season or not," he said. "In the performances we had what you'd want from a top team - we had structure, talent in the team and then you have work.
"That mentality to work and run with talent and structure gives you a great chance. I look at Kyogo's goal, we made about 23-24 passes - to have that confidence and personality and wait for the moment.
"Across the board I am really, really happy with the performances. And with the younger guys coming into the game there was no difference, they pressed the game, they harassed the opponent and then showed their quality when we had the ball."
There were a couple of fitness issues to arise from the game. Nicolas Kuhn was left out because of a back strain and Daizen Maeda went off with a knee knock, but both wide players are expected to be fit to face Killie.