MIAMI -- Luis Valbuena, subbing for the injured Emilio Bonifacio, led off for the third time this season and second game in a row on Monday as the Cubs opened their series against the Marlins.
Bonifacio, who has led off all but 11 games this season, went on the disabled list Friday with a right oblique strain.
Heading into Monday's game, Valbuena is 2-for-8 as the leadoff man. In his last 26 games, he was batting .360 with 11 doubles, three homers and 10 RBIs.
"We'll see how he handles it," Cubs manager Rick Renteria said of Valbuena.
The Cubs' other options include Junior Lake, who is 2-for-13 batting first and has a .268 on-base percentage overall.
Rondon strikes out the side in return to action
MIAMI -- Hector Rondon finally got to pitch.
The right-hander pitched one scoreless inning of relief on Monday in the Cubs' 5-4, 13-inning win over the Marlins. He struck out the side in his first appearance since June 6.
Rondon, the designated closer, had some tenderness in his right elbow, and the Cubs wanted to be careful. He had pitched in four straight games in mid-May, but has been in only three games this month.
"He's good to go," Cubs manager Rick Renteria said. "We had an opportunity to go and use Neil [Ramirez on Sunday], and give Hector another day. We could've used him yesterday."
Rondon was shut down last week and threw a bullpen on Saturday. The right-hander had Tommy John surgery on his right elbow in 2010. Will the Cubs be more careful?
"I think, more than anything, we'll just see how he is on a daily basis," Renteria said. "I'm not going to limit or put a limit on where he's going to be. We'll just monitor all of them normally and see how he is the next day."
Ramirez has filled in well, picking up saves in his last two appearances Friday and Sunday against the Phillies.
"The look in their eyes is pretty convincing that they know what they want to do," Renteria said of the young relievers. "Neil has done a great job."
Baker, Renteria mourn 'wonderful' Gwynn
MIAMI -- Catcher John Baker talked to Tony Gwynn Jr. on Sunday when the Cubs were wrapping up their series against the Phillies, and had asked for an update on the outfielder's father, who was battling cancer.
"He said he thought he was doing much better," Baker said Monday.
On Monday, Hall of Famer Tony Gwynn died after a long battle with salivary gland cancer. He was 54.
"For me, the day after Father's Day -- that's the hardest part for me is to think about Junior," said Baker, who played for the Padres from 2012-13 and got to know father and son.
"Tony still talked to you like a regular person, which I think sometimes doesn't happen with some of the superstar players and the Hall of Famers," Baker said. "Tony talked to you man to man, eye to eye about real things. I really appreciated his presence and him being around.
"He's one of the greatest hitters in the history of baseball, plus he was really nice," Baker said. "Then I get to meet his kid and see how he was raised and see what kind of person Tony Gwynn Jr. is, and I'd like to think it's a great example of what a father is supposed to be because of the child he raised. It's a really sad day for baseball."
Cubs broadcaster Jim Deshaies was saddened by the news. Gwynn had more hits off Deshaies than any other batter (18), and was 18-for-52 (.346). Former Cubs pitcher Greg Maddux posted on Twitter: "Tony Gwynn was the best pure hitter I ever faced! Condolences to his family." Gwynn batted .429 (39-for-91) off Maddux, and the pitcher never struck him out.
Cubs manager Rick Renteria spent six seasons on the Padres' Major League staff, and he also managed in San Diego's Minor League system. He knew how much impact Gwynn had on the team.
"Tony Gwynn was the Padres," Renteria said. "Here's a guy who spent his whole career there, did a lot of good there, was a tremendous player. His son ... if he's any reflection of his father, he'll be a wonderful person."
Renteria never talked hitting with Gwynn.
"He was a great, great hitter, and a great baseball player, and obviously, a Hall of Famer," Renteria said. "As much as everybody will miss the baseball player, the man will be missed even more."
Baker didn't ask for hitting tips either, but Gwynn gave them. However, they weren't intended for the catcher.
"He talked to me more about some of the other left-handed hitters on the team," Baker said. "It shows his genius -- he knew some of the younger players would listen to me when I talked to them, and maybe they'd be turned off if Tony Gwynn told them something.
"There would be a couple times when he'd come up to me and sit down and tell me what he wanted Yonder Alonso to start doing," Baker said. "He'd try to get me to relay the information in a different way. He'd say, 'I've told him the same thing, but maybe if he hears it from you, it'll sink in."
• When the Cubs signed first-round Draft pick Kyle Schwarber under the slot, they hoped to use the extra money toward the prep pitchers selected in the First-Year Player Draft. On Monday, there were reports that the team had reached agreement with two of their picks, including high school left-hander Carson Sands. Sands has reportedly signed for $1.1 million; the money slotted for the 109th pick was $480,600. The Cubs also have reportedly agreed to terms with 11th-round pick Jordan Brink, a right-handed pitcher. He reportedly received a $100,000 bonus. Both players need to undergo physicals before the deals will be announced by the team.
• Double-A Tennessee's Kris Bryant hit 16 home runs, including four in the final round, to win the Southern League Home Run Derby Monday night in Chattanooga. Bryant, who will start at third base and bat third for the North Division in Tuesday's All-Star Game, beat Mobile's Jonathan Griffin in the final round.
• Renteria played for the Marlins from 1993-94, and the Cubs manager earned the nickname "The Secret Weapon" for his versatility and pinch-hitting ability.
"They're great memories," Renteria said of his days with the team. "At that time, being a new club here in Miami, the ballpark was packed, and there was excitement for the team, and it was a lot of fun, lot of energy."
Renteria played second, third and left field for the Marlins, and batted .250 in two seasons.
• Class A Kane County completed one of the most successful halves of a season in the 24-year history of the franchise, compiling a 45-25 record. Only the 2001 Cougars, which won the Midwest League championship and included present-day Major Leaguers Miguel Cabrera and Adrian Gonzalez, have won more games in one half of a season with 47 wins in the first half that year.
Playoff tickets go on sale Thursday, starting at 9 a.m. CT. The Cougars open the playoffs on Sept. 3.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.