Stekelenburg and Gazzaniga are competing to play in goal for Southampton in their match on Boxing Day against Arsenal.
The Dutch stopper has been the Saints’ first choice in goal so far this season, with Fraser Forster currently out injured, but he has missed the south coast’s side’s last two matches.
In his absence Gazzaniga has stepped in, and Stekelenburg admits that his Argentine teammate has performed well against Crystal Palace and Tottenham Hotspur.
“Well if you see him as I do in training he’s doing very well and in the games he played he did very well,” he said.
“It’s always difficult when you’re not playing a lot. He played a few games for the under-21s. He did well there as well so of course it’s difficult for him.
“That’s the position you’re in as a goalkeeper. Only one can be playing.”
Southampton actually lost both their matches against Palace and Spurs, but without Gazzaniga between the posts the defeats may have been much heavier.
The former Gillingham man made some excellent saves in both contests and he proved his worth to the team time and again.
However he does lack the experience of Stekelenburg, so Koeman may opt to select the Fulham loanee at the Emirates Stadium now he is back.
In truth, neither Stekelenburg or Gazzaniga are likely to hold on to their spot in Southampton’s line-up for much longer, as Forster returned to training on Tuesday as he steps up his comeback from a long-term injury.