"It ended up working out all right," Marshall said.
Piniella pulled an unusual double-switch, moving the pitcher to the outfield for one batter because Marshall is the only lefty in the bullpen and the Cubs didn't want to lose him.
Here's what happened: Angel Guzman started the ninth, and the first two Cardinals batters got on base via a hit and an error. Guzman was lifted for Marshall, who walked pinch-hitter Nick Stavinoha to load the bases.
Piniella then moved Marshall to left field and pulled outfielder Alfonso Soriano from the game. Aaron Heilman came in to face right-handed-hitting Brendan Ryan and struck him out.
Piniella then made another double-switch and put Marshall back as pitcher, and Reed Johnson was inserted into left field. Marshall struck out pinch-hitter Jarrett Hoffpauir. Colby Rasmus then lofted the ball to left, and Johnson made a diving catch to end the inning.
"It was fun to be a part of that, no matter how it turns out," Cardinals manager Tony La Russa said. "It takes creativity and it takes guts, and Lou showed both of them."
Piniella said the Cubs have done it before, but they did so before he was the manager. You have to go back to June 13, 1990, in a game against the New York Mets when Les Lancaster pitched the sixth, then was moved to left in the seventh for three batters, then returned to the mound.
Was Marshall surprised?
"A little bit," Marshall said. "When [Piniella] said it, it made sense. I knew who was coming up for the next two hitters. It was funny to watch Heilman pitch that at-bat because he was throwing so many pitches inside. I was like, 'If he does hit it, it'll be right at me, and hopefully I can make the play and maybe throw somebody out.'"
The Cubs pitchers are required to shag flies in the outfield so they are prepared for anything. In the last game before the All-Star break and the second game of a day-night doubleheader, anything goes.
"I think I could've handled it," Marshall said about making a defensive play so far from the mound. "In high school and Little League, I played outfield. It wasn't completely unfamiliar to me. In the big leagues, it's a lot faster. Heilman did a great job of getting that guy out and gave me a chance to come in and finish the inning."
As Marshall headed out to left, some of the Cubs relievers joked with him. He had to break the news to Soriano, who was a little confused at the sight of the lefty trotting toward him.
"It probably caught him as off guard as it caught me," Marshall said.
When Marshall returned to the mound, he wasn't sure if he could throw a couple of warmup pitches.
"I didn't know what the Major League rules were," Marshall said. "I saw Larry [Rothschild, pitching coach], and he was [saying], 'Just warm up again.'
"[Being in the outfield] wasn't completely unfamiliar to me. It would've been funny if [Ryan] hit a shallow sac fly and I could've thrown out [Yadier] Molina at home plate. It would've been icing on the cake. I wish we could've gotten a win."
The bleacher fans responded appropriately.
"They were funny -- they were chanting, 'We Are, Mar-shall,'" Marshall said.
The Cubs already were playing somewhat short-handed after catcher Geovany Soto was placed on the disabled list on Saturday. Jake Fox, the emergency catcher, entered the game defensively in the eighth.
"It was cool to get back there again, it was cool to put all the gear on," said Fox, a hitter who has been trying to find a regular position. "It was a blast."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.