Marouane Chamakh scored on his home debut but Arsenal had to settle for a 1-1 draw against AC Milan in the Emirates Cup.
The Morocco striker - a free transfer from Bordeaux - produced a neat finish to put the Premier League side ahead just before the break.
However, Arsene Wenger's young Gunners were eventually pegged back when Pato nodded in a free-kick with 14 minutes left and on Sunday face the challenge of Celtic, who drew 2-2 against Lyon earlier.
As expected, Wenger had named a mixed starting XI, with new signings Chamakh - who netted his first Arsenal goal in the midweek win 4-0 over SC Neusiedl in Austria - and Laurent Koscielny making their first appearance at the Emirates Stadium.
Thomas Vermaelen was captain, standing in for Cesc Fabregas - the Barcelona target still on extended leave after the World Cup - while there were also chances for youngsters Jack Wilshere, Kieran Gibbs and Emmanuel Frimpong to impress ahead of the new season, which begins at Liverpool on August 15.
However, there was no place in the squad for Manuel Almunia, whose place as number one is in doubt, as Lukasz Fabianski started and fellow young Pole Wojciech Szczesny was on the bench.