When introduced at the Cubs home opener on Monday, Marmol was booed by the crowd of 40,083. He was booed again when he entered the game in the eighth and served up a double to Milwaukee's Ryan Braun on a first-pitch fastball.
"I'm not the first one, [I won't be] the last one," Marmol said. "I'm fine. I'm trying to do my job and trying to get people out. That's what I need to do."
After Braun's double, Marmol struck out Rickie Weeks, walked Jonathan Lucroy, which prompted more boos, struck out Alex Gonzalez and got Martin Maldonado to ground out to end the inning.
"I felt good getting those last people out," Marmol said. "It's been tough for me to get three outs and put a zero on the board and I did it."
Cubs manager Dale Sveum said it was tough to hear the fans razz Marmol.
"You're with these guys every day and you know who they are behind the scenes and the adversity they have to go through," Sveum said. "On Opening Day, to get booed like that isn't fun for anybody. Bringing him in the game, he had to [hear] it twice in one day. It's unfortunate, but that stuff happens. It's tough for all of us in that clubhouse to see it."
As for the outing Monday, Sveum said it was encouraging to see Marmol throw his slider for strikes and escape any further damage after Braun's hit.
Theo Epstein, Cubs president of baseball operations, supported Sveum's decision to make Kyuji Fujikawa the closer in place of Marmol.
"I think he made the right call," Epstein said prior to the Cubs' 7-4 loss. "Marmol bounced back last year to have a really solid second half. Of course, he should've started this year as our closer. You don't lose your job after two bad outings at the end of Spring Training. To do that would be counter to everything we believe in.
"He pitched really poorly three times to start the year," Epstein said. "It was important for the team to make a change. We need to believe we can win these close games late. For Marmol, last year, he went back after struggling, fixed himself and came back and contributed. We need to be open to that possibility again."
Sveum said they want Marmol to work on his pitch selection and not get "fastball happy."
"He had a wipeout slider at one time in his career, and now it's not as consistent but it's still his out pitch," Sveum said of Marmol. "He needs to throw fastballs but still understand you're a slider pitcher. If things go awry, get back in counts with fastballs, but let's not get away from our bread and butter either."
Marmol has given up five earned runs on six hits and two walks over 1 2/3 innings in three games, and served up a game-tying home run to B.J. Upton and a walk-off homer to his brother, Justin, on Saturday in Atlanta.