With a 15-6 record, Taijuan Walker is why they don't decide the Cy Young based on record anymore.
Walker was Captain Rollercoaster in his first year with the Phils. Through his first 11 starts, he sat at over a 5.00 ERA. In June, he went 5-1 with a 1.50 ERA. In July, he had a 3-1 record with a 3.86 ERA. He was never the reason this team won games, but he was always a reason that they won (or sometimes lost) games.
Most of Walker's starts relied on his splitter. If his splitter was going, he was going. His splitter was swung at with a 24.5 percent whiff rate and an 18.2 percent putaway rate. He could use it when he was behind in counts to steal a strike, when he could keep it on the corner. It was when his splitter found more than a little bit of plate that he ran into issues. He could also use it to get swings and misses down in the zone. Again, when he kept it down, he was successful.
Over the course of 31 games, Walker collected 138 strikeouts, pitching to a WHIP of 1.309, right around the league average.
The other issue Walker had was his slow starts. He was notorious for giving up multiple runs in the first one or two innings and then settling in for the next three, or four. That's okay in the regular season when you're trying to eat chunks of innings and keep games close. Down the stretch and into the playoffs, it becomes a problem.
This is why Walker was only seen at the top step of the dugout throughout the postseason.