For illustration, the Chelsea second choice keepers in the last three seasons have played the following:
14/15 Cech played 15 matches (7 PL, 4 League Cup inc the FINAL, 2 FAC, 2 Champions League)
15/16 Begovic played 25 matches (17 PL, 2 League Cup, 1 FAC, 5 Champions League)
16/17 to date...
All of this.
And even if Cortois never gets injured or suspended or suffers a loss of form or goes on strike or gets kidnapped, the number 2 would still expect to play:
4 or 5 League Cup matches
3 or 4 FA Cup matches
2 or 3 'dead rubber' CHAMPIONS LEAGUE group matches
Its not like he'd NEVER...
Of course they would, but if that injury occurs on September 1st, there are four months until that window. The back up keeper will get an opportunity at some point - he might back himself to grab it with both hands.
Not really. Very few clubs have the spending power to pay stupid money for a back up player, and no others with a training ground a comfortable commutable distance from Stockdale's house.