Van Slyke's walk-off home run lifted the Dodgers to a 5-3 win over the Marlins, who had gained a one-run edge in the top of the ninth on Christian Yelich's two-run homer.
"This is about as low as I can get," Cishek said. "This is a huge trial in my life right now, obviously, career-wise. I've always found a way to get out of it. I'm waiting for that time to come."
The misery Cishek felt Monday came a day after he gave up two runs in the ninth inning in a 3-2 loss to the Giants at AT&T Park.
Cishek now has converted just three of his seven save chances, and his ERA has ballooned to 10.32 ERA -- 13 runs in 11 1/3 innings.
Manager Mike Redmond noted he likely will mix and match. A.J. Ramos, Bryan Morris and Mike Dunn are options.
"Shrek [Cishek] has done a tremendous job for us, but at the end of the day, it's about winning games," Redmond said.
A year ago, Cishek converted 39 of 43 chances. The sidearm-throwing right-hander has already blown as many as he did last season.
"It's tough to win in the big leagues, and when you get late leads, you've got to be able to lock them down," Redmond said. "Against a team like the Dodgers, they have so many weapons, great pitching. You know you're not going to get a lot off those guys. To have a lead in the ninth, you've got to be able to finish them."
The Marlins are now 3-5 on the road trip, with three blown saves. Along with the past two games with Cishek, they opened their swing losing, 6-4, at Washington, with Morris giving up four runs in the eighth inning, after Miami went up, 4-2.
"I don't know. We'll figure it out," Redmond said. "We can't keep blowing late leads. That's the third lead we've had. We had one in Washington we weren't able to lock down also. We weren't mixing and matching trying to get to the ninth."