What has he done to suggest he'd make things ugly? From all indications, that's not his MO.If he makes things ugly and sits out next season, he'll have started 11 games of football between turning 23 and moving to Bayern at 25y 6m with an ACL in between.
2 and half years with no football.
He'd play when Pep says he should play. And sit on the bench when instructed to do so. The only people that might make it ugly would be management and Pep. But that would be pretty of them, so I doubt they'll do that.
At this point, Sane has nothing to fight over. He either leaves this summer, in January or definitely next summer.
The first 2 depends on City and Bayern, the last an inevitable conclusion if the first 2 fails.