Things livened up quickly after the break when Moses put Chelsea ahead.
From the free-kick that followed, Kolasinac rose to head into the bottom corner from Xhaka's precise delivery to send the match to penalties. Team A then get two successive penalties, a little like the tie-break in tennis, and so on until there is a victor.
After Gary Cahill's opener for Chelsea was cancelled out by Theo Walcott, Arsenal defender Nacho Monreal stepped forward, correctly, to take his kick.
The penalties took a dramatic turn when surprise-taker Courtois, and then Morata, both missed the target, allowing Oxlade-Chamberlain and Giroud to seal victory for the Gunners. And going second in the rejigged shootout, Arsenal overwhelmed Chelsea 4-1 to win the traditional curtain raiser to the English season after the match was locked at 1-1 after 90 minutes.
If that was a tricky call for Madley, his decision to send off Pedro with 10 minutes remaining was more straightforward.
"There are six teams in England and all of them can fight for the title".
"We had the intensity in the games in our preparation that is needed to be ready", said Wenger. "We had some hard moments at the start of the second half but after [that] we dominated the game".
"If you look at the Premier League there are ten teams that can win it - we need to maintain our togetherness".
"I didn't see the situation with the sending off".
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"For sure there is a bit of frustration, but you know very well we have to respect referees decisions". This is the second game, after the FA Cup [final], that we finish with 10 men.
Conte refused to be drawn on either the red card incident or Willian's booking for simulation in the penalty area before half-time, claiming not to have seen either flashpoint clearly.
"We might go through some very good periods and some not so good periods".
"In the Premier League every game is a battle like today".
The Gunners have lost on the opening day in three of the last four seasons.
The second controversy was the straight red card shown to Pedro which led immediately to Arsenal's equalising goal.
There were just 82 seconds between Pedro's red card and Sead Kolasinac's equaliser. "Don't forget today Arsenal didn't play with many players, strong players".
After a strong first half, Arsenal fell behind to a Victor Moses goal in the 46th minute.
Arsenal kick off the new top-flight campaign when they host Leicester City on Friday (19:45 BST).
The Italian was referencing Jose Mourinho's Chelsea finishing mid-table in 2015-16 the year after lifting the title.
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