By Walter Villa, The Sports Xchange

MIAMI -- In just seven major league games, Willson Contreras already has eight RBIs, including the game-winner on Friday night at Marlins Park.

He also hit a two-run homer, his third long ball in his amazing first week in the majors, as the Chicago Cubs beat the Miami Marlins 5-4.

"It's like oxygen," Cubs manager Joe Maddon said when asked to describe Contreras' contributions so far. "It's absolutely necessary."

Does the rookie get nervous?

"No," said Contreras, a 24-year-old native of Venezuela who is quickly becoming a cult hero in Chicago. "I have confidence in myself. I'm just trying to have fun."

Contreras is surely enjoying himself, hitting a homer in the first inning and a go-ahead, run-scoring single in the seventh.

Both hits went to right field, but Contreras said he's not making an effort to go that way. He's just trying to make hard contact.

Defensively, Contreras is a catcher, but he played first base on Thursday and again in the later innings on Friday, and he said he is willing to play second if Ben Zobrist needs a break.

Zobrist was hit by a pitch on a foot on Friday, suffering a contusion.

"Ben's really sore," Maddon said. "It would be a reach to think he could play Saturday."

Maddon added that first baseman Anthony Rizzo (back) was ready to pinch-hit on Friday.

Rizzo and Miguel Montero (knee) are likely to return to the starting lineup on Saturday, but the Cubs want to find a spot in the lineup for Contreras, who went 2-for-4 to raise his batting average to .412.

Contreras' heroics helped the Cubs (48-24), who have the best record in baseball, snap a season-worst, four-game losing streak. They have split the first two of a four-game series against Miami (39-35).

But Contreras wasn't the only hero.

Third baseman Javier Baez made a spectacular catch on a foul ball. Baez, who fell face-first into the stands after making the grab, stayed in the game.

In addition to that grab, four Cubs pitchers combined to hold Miami to two hits.

Both starting pitchers -- Miami's Tom Koehler and Chicago's Kyle Hendricks -- got no-decisions.

Hendricks went five innings and allowed just one hit. But that one hit was a grand slam by Justin Bour, whose shot was preceded by two walks and an error.

Hector Rondon pitched 1 1/3 scoreless innings for his 13th save of the season and his first since June 18. Reliever Trevor Cahill (1-2) got the win after pitching a scoreless sixth. And Travis Wood (1 2/3 innings) bridged the gap to get to Rondon.

Chicago and Miami each scored four runs in the first inning, the first time in the majors this season that two teams had scored at least that many in the first.

The Cubs' outburst started with Kris Bryant's one-out solo homer to left. Bryant pulled an inside fastball for his 18th homer of the season.

After a single by Zobrist, Contreras hit his blast. Chris Coghlan then pulled a triple down the right-field line, scoring on a Baez single past a draw-in infield.

Bour's grand slam to center field tied the score. It was his 13th homer of the season and his second career grand slam.

All four of Miami's runs were unearned because the rally started with a fielding error by shortstop Addison Russell. Hendricks compounded his problem by issuing two consecutive two-out walks to load the bases.

The 4-4 score felt like a reprieve for Koehler.

"It's not often when you have a first inning like I did that you can get a reset," Koehler said. "You get a do-over."

That "do-over" was in effect until the seventh. Working against reliever Mike Dunn (0-1), Bryant walked, advanced to second on the Zobrist hit-by-pitch and scored on Contreras' one-out single.

"I was trying to go in and I missed away," Dunn said of his pitch to Contreras. "I had no command tonight. Everything I threw wasn't even close."

As for Contreras, it appears he's in the majors to stay, which is the message he conveyed to his coaches at Triple-A Iowa when he was called up to the Cubs on June 17.

"I told them that once I get here I'm not going to go back because this is where I want to be," Contreras said. "Even if I go 0-for-4, I'm going to do everything I can for my team behind the plate."

Or, if called upon, he will do everything he can at first base, second base or anywhere else he's needed.

NOTES: Miami CF Marcell Ozuna entered Friday leading National League outfielders in OPS. ... Miami, hoping for a postseason run, might skip RHP Jose Fernandez a second time this year, which could allow him to pitch potential playoff games. The Marlins don't want to exceed 180 innings this year on Fernandez, who is in his first full season after elbow surgery. His next start is Sunday against Chicago. ... After going 23-0 in starts by RHP Jake Arrieta, Chicago is 2-3 in his past five. Arrieta faces the Cincinnati Reds on Monday. ... Cubs RHP Joe Nathan, 41, reported to Double-A Tennessee to begin his rehab assignment. The six-time All-Star, who signed last month, has impressed Chicago with his recovery from a second elbow surgery.