"Just forget about this one and bounce back tomorrow because we cannot be perfect," said Strop, who walked two and threw a wild pitch in the inning. "We gave it our best. It didn't work."
The Cubs were trying to go undefeated on a homestand of six or more games for the first time since going 7-0 from May 26 through June 1, 2008, against the Dodgers (3-0) and Rockies (4-0).
"These guys should keep their head up," Renteria said. "They are very disappointed right now because we felt like we were on the cusp of being able to have a perfect homestand. They certainly were trying to do it."
Jake Arrieta tossed six scoreless innings, allowing just three hits and fanning seven with no walks.
"The command has tightened up considerably over the past year," Arrieta said. "I still would like to become even better in certain areas, continue to improve the command of off-speed pitches, and obviously the fastball."
Marlins starter Henderson Alvarez went 51/3 innings before leaving with a hip injury in the sixth. He was charged with two runs (one earned) while striking out five and issuing no walks.
"Alvarez is no easy pickings," Renteria said.
Starlin Castro lined a one-out double to left-center in the sixth. Luis Valbuena was safe on an error by first baseman Garrett Jones as Alvarez strained his left hip trying to cover the bag at first. Dan Jennings took over for Alvarez and yielded a two-run triple to Nate Schierholtz to make it 2-0.
"We played pretty good here. Hopefully we will stay like that on the road too," Castro said.
The Marlins tied the game in the seventh on RBI hits by J.T. Realmuto and Adeiny Hechavarria against reliever Brian Schlitter.
The Cubs loaded the bases in the seventh. Pinch-hitter Darwin Barney was hit by a pitch before being sacrificed to second by Emilio Bonifacio. Junior Lake deposited a double just inside the rigtht-field line and Anthony Rizzo was walked intentionally.
Left-hander Mike Dunn was summoned to face Valbuena, who drew a walk to force in a run.
The Marlins regained the lead 4-3 in the eighth when Jones delivered a bases-loaded sacrifice fly to tie the score. After Marcell Ozuna was walked intentionally to reload the bases, Strop uncorked a wild pitch to allow the go-ahead run to score.
Despite Sunday's disappointment, the Cubs are focused on the bigger picture as they embark on a 10-game trip to Pittsburgh, Philadelphia and Miami. The Cubs are 10-21 on the road, compared to 15-14 at Wrigley Field.
"The only way we can win on the road is if we keep playing the same like at home," Castro said.
"The reality is that if you are at home or on the road … obviously we just had a very good homestand," Renteria said. "I am very proud of how we attacked, overcame and tried to win every single ballgame we had a chance to. When we are on the road, we are going to try to do the same thing.
"During the (winning) streak we all know that a lot of things come into play. You have to have pitching and defense and clutch hitting, and sometimes you have to overcome deficits. And hopefully we can get on the road trip in Pittsburgh (Monday night) and carry the confidence we had throughout this homestand."