The Gunners' summer signing featured prominently ahead of their clash with Manchester City, while the Costa Rica forward also saw plenty of action.
Ahead of an important Premier League game, it's always good to receive a boost or two in training.
And, on that front, Arsene Wenger will be reasonably pleased with his side's training session on Wednesday afternoon. Indeed, Arsenal were able to put goalkeeper David Ospina and forward Joel Campbell, in particular, through their paces ahead of their clash with Manchester City on Saturday.
The Gunners host the defending champions at the Emirates Stadium during the day's early kick-off on the back of two consecutive draws, at Everton and Leicester City respectively. The north London side also failed to beat Man City last season, drawing with them at home and losing 6-3 away.
But Wenger and co. will be delighted to have seen summer signing Ospina in proper action on the training ground ahead of their big clash. The Colombia goalkeeper was brought in to deputise for Wojciech Szczesny should he have to sit out due to injury, suspension or form and will likely provide stern competition for the Polish shot stopper throughout the campaign.
Campbell, meanwhile, has seen little game time so far this term but may be required by Wenger in the coming weeks, with Champions League football returning to Arsenal's schedule.
As well as Ospina and Campbell, the likes of Mikel Arteta, Szczesny, Santi Cazorla, Per Mertesacker, Laurent Koscielny and Lukas Podolski were also in action at Arsenal's training ground at London Colney. Here are the best images from the Gunners' practice session...