The Swiss centre-back, virtually ever-present over the past four years, has found himself among the substitutes for the last two league matches against Everton and Tottenham, with Dan Burn stepping in alongside Malick Thiaw.
Schar's battle to reclaim his place stems from a concussion suffered against Barcelona, an injury that ruled him out for three matches.
Before that setback, he had featured in Newcastle's opening five fixtures of the season, contributing to three clean sheets and maintaining his status as a defensive mainstay.
His absence opened the door for Thiaw, the 35-million-pound off-season signing who has delivered a series of assured displays since breaking into the team.
Although Schar returned for a cup tie against Tottenham and later regained his spot in the league for the impressive victory over Manchester City - where he played a key role in subduing Erling Haaland - his time back in the side proved short-lived.
He also featured in the following match against Marseille, yet has again been relegated to the bench for Newcastle's most recent outings.
"Being on the bench has been quite difficult actually," he said.
"It wasn't an easy situation. I think I did pretty well at the start of the season. Then I had the concussion, out for three games, and I hadn't done anything wrong or played bad - but it's very hard to get back in the team.
"It's very difficult, it was a new situation which has never been the case in the last four years. A lot of things which were new and not easy.
"It's something I know will happen because I'm getting older but I don't want it to happen. I still feel I can bring a lot to the team.
"I just want to be on the pitch and do the same thing I've tried to do over the last seven years and leave my heart on the pitch."