Giroud had an extended break following Euro 2016 and did not return to full training before the season kicked off.
As a result the Frenchman has made just three appearances for the Gunners this term and is yet to start a single game.
“If I was Olivier Giroud, I'd be a little concerned not to have started against Paris Saint-Germain," Keown wrote in his Daily Mail column.
“Going with Alexis Sanchez shows that Wenger wants pace in that central position.
"He was sent off against PSG and he might have gone on a little too fired up wanting to prove why he should start."