"When it counts" - there's lots of games he pitched in "when it counted". Not the playoffs, obviously, but the Braves were fighting for their playoff lives all September. Here's what he did in September:
9/3 vs Col - 7.0 ip, 6 h, 0 r, 0 er, 0 bb, 9 k, 3-0 victory (Sale got the W)
9/8 vs Tor - 6.0 ip, 2 h, 0 r, 0 er, 1 bb, 7 k, 4-3 victory (Sale got a ND, the game went to extras)
9/14 vs LAD - 6.0 ip, 5 h, 1 r, 1 er, 2 bb, 6 k, 10-1 victory (Sale got the W)
9/19 at Cin - 5.0 ip, 5 h, 2 r, 2 er, 2 bb, 6 k, 15-3 victory (Sale got the W)
So: 4 starts, all 4 games won by Atlanta, 2 of which were coming off a loss in the previous game, and Sale put up this stat line:
3-0, 24.0 ip, 18 h, 3 r, 3 er, 5 bb, 28 k, 1.13 era, 0.96 whip, 10.5 k/9
I mean, those games, for Atlanta, were absolutely "when it counted", and Sale stepped up big time.
He also - which goes to your point about not being able to count on him - missed his last regular season start and obviously the playoff game. So that 9/19 start at Cincy was his last game - the team went two full weeks without him throwing a single pitch.
But he absolutely did come up big in games that definitely "counted" for the Braves (and yes they all "count" but those were September games in the heat of a playoff race, when Atlanta desperately needed wins).