Andrew Saalfrank's performances throughout the postseason have actually been pretty respectable; with 3 1/3 pitched cumulatively, he's only allowed three hits. But he does have a weakness: he's been walking batters. To be fair, Saalfrank is a rookie who was only called up at the beginning of September, and his 10 1/3 innings pitched during the regular season were almost spotless (only two earned runs given up on seven hits).
However, with eight walks over his postseason innings, he's walked more hitters he's faced than any other Dbacks bullpen pitcher this postseason. His three back-to-back-to-back walks to Kyle Schwarber, Trea Turner, and then Bryce Harper in Game 4 loaded the bases and led to a two run single by Alec Bohm to put the Phillies up 4-2. It's unsavory situations like this that the Dbacks won't be able to afford in the World Series.