Chelsea's sluggish pre-season preparations for the defence of their Premier League title continues at Wembley this afternoon when they were downed by an Alex Oxlade-Chamberlain first-half shrike as FA Cup holder Arsenal won 1-0.
Out in the USA, Chelsea failed to win any of their three games in regulation time - going down 4-2 to New York Red Bulls before seeing off on penalties, Paris St-Germain and Barcelona, having drawn 1-1 and 2-2 respectively.
With Diego Costa, absence from the squad entirely - his hamstring, once agin, failing him, the Boues opted for Loic Remy up front.
He failed to impress as did his replacement Radamel Falcao, who played the second half.
QPR's Charlie Austin is still on Chelsea's radar but with West Ham United about to put in a £15milliom bid for the Chelsea-supporting striker, the Blues had better act quickly if they are to bolster their striking options.
As for the action on the pitch, Chelsea had a shout for a penalty turned down on eight minutes when Cesc Fabregas toed the ball ahead of Per Mertesacker, who stood on the midfielder's boot and then shouldered him to the ground, all inside the Arsenal penalty area.
Referee Gary Beswick simply played on.
Both sides then enjoyed a spell of possession, with neither looking to threaten the oppositions' goal.
Finally, on 23 minutes the first attack on goal and it came from the head of Walcott, who glanced on a free-kick, however Courtois was more than equal to the task, contemptuously plucking the ball out of the air and to safely.
But with their second effort, two minutes later, they did score. Alex Oxlade-Chamblain, cut in from the right and sent in high and wide of Courtois the perfect left-footer that arrowed into to the top corner of the net, to put the Gooners one-nil up.
Chelsea enjoyed their best spell of pressure after that setback, and were unlucky, on 33 minutes to see a curling right-footed effort by Ramires, from just inside the Arsenal penalty area, inch past Cech's righ post. The former Chelsea goalkeeper stood no chance had the ball being a couple more inches to his left.
Quite how Ramires failed to equilateral two minutes later bemused Jose Mourinho, who, from the sideline demonstrated the perfect downward header stance, that the Brazil midfielder, unfettered from any challenge somehow headed over the Arsenal crossbar despite being just six yards out.
Branislav Ivanovic produced a fine last-gasp header to thwart Arsenal as the minutes ticked down to half time.
Mourinho took decisive action at the break, replacing Ineffectual Loic Remy for on-loan hit-man Radamel Falcao, Arsenal remained unchanged.
It took just eight minutes of the restart for Mourinho to haul off Ramires for Oscar. The Brazil midfielder had the next attempt on goal, but his 25-yard daisy-cutter went well wide of Cech's right post.
Eden Hazard should have equalised on 62 minutes but took one touch too many inside the Arsenal area and screwed his shot wide of goal - he was put off by the last-ditch lunge of Laurent Koscielny
The first yellow card of the match went to Chelsea left back Cesar Azpilicueta for hacking down Oxlade-Chamberlain.
Arsene Wenger made his first change a minute later, bringing on striker Oliver Giroud for Walcott.
Francis Coquelin then received a yellow for fouling Hazard.
Cech then produced a brilliant save from Oscar's free kick.
In the space of 60 seconds, Kurt Zouma replaced Azpilicueta while the Chelsea defence failed to pick up Giroud who squandered a gilt-edged chance to double the lead hacking the ball over Courtois's goal from close range instead.
A looping header by Zouma on 74 minutes failed to trouble Cech.
Mourinho, needing to get a goal, replaced centre-back John Terry for winger Victor Moses on 81 minutes, changing formation to three men at the back.
Courtois spared Chelsea blushes by preventing Santi Cazorla and the Aaron Ramsey as the Gooners attacked the Blues in the counter-attack.
An Ivanovic header going well wide with seconds on the clock summed up Chelsea afternoon - not quite up to the required speed or sharpness needed.
Chelsea have a final match at the Bridge, on Wednesday when they face Fiorentina before the home opening league match, against Swansea City on Saturday.
Teams: Chelsea, Courtois, Ivanovic's, Fabregas, Ramires, Hazard, Remy, Matic, Willian, Cahill, Terry, Azpilicueta
Subs, Begovic, Zouma, Oscar, Falcao, Cuadrado, Mikel, Moses
Arsenal, Cech, Mertesacker, Koscielny, Ozil, Walcott, Oxlade-Chamberlain, Ramsey, Monreal, Cazola, Bellerin, Coquelin
Subs. Dubuchy, Gibbs, Gabriel, Arteta, Giroud, Martinez, Iwobi
Referee
End so