Koch, 28, has had an up-and-down season; showing flashes of dominace on some days, while showing a flat 90-MPH fastball on most days.
It all has led to a poor 5.30 ERA and just 11 saves in 15 chances, which isn't bad if you were to ignore the 56 baserunners he's allowed in less than 40 appearances and 37 1/3 innings.
Koch has not allowed a baserunner in just 12 of those outings, an amount far too high for a closer expected to shutdown the opposition in close games.
The erratic Koch is on pace to save just 21 games and blow eight, which would be career low's for the right-hander whose lowest save total of 31 came back in his rookie year of 1999.
Koch had a 144 career saves in four season's heading into this season.
Manuel has not officially bounced Koch from the closer role, but reports have Tom Gordon getting the next few chances.
Koch was acquired over the off-season, along with lefty prospect Neal Cotts and outfielder Daylan Holt, from the Oakland A's for Keith Foulke, catcher Mark Johnson and minor league closer Joe Valentine.