The expectations for Riddle, who made his first big league start in Tuesday's 8-4 win over the Braves, is to execute the basics.
"Just to be bread and butter," Marlins manager Don Mattingly said. "He's a kid with a low heartbeat. He seems to be pretty calm. He didn't look too overwhelmed in Spring Training. His growth from one Spring Training to the next was pretty huge."
Prado, who is on the DL with a right hamstring strain, began his rehab assignment on Wednesday for Class A Advanced Jupiter. The plan is for the 33-year-old third baseman to play five innings on Thursday and seven innings on Friday and Saturday.
There is a chance Prado could be reinstated on Sunday for the series finale with the Mets at Marlins Park. Miami is on the road at Seattle on Monday, and Prado could be on that trip.
Hechavarria, on the DL with a left oblique strain, is set to do some hitting off a tee in the cages on Thursday.
• Mattingly and the staff are stressing the importance of add-on runs, which the club has done effectively for the most part during the first week of the season. The Marlins are hoping to create a mindset of continuing to score with leads, rather than easing up at the plate.
"There's a lot of games and a lot of at-bats," Mattingly said. "You're going to have days where you're giving some at-bats away or you're not feeling good. I think the mentality [should be] moving forward all the time. You can't take things for granted. One day taking your foot off the pedal can turn you into having a bad habit. The next thing you know, that turns into four or five games."
• Tyler Moore, who made his first start of the season at first base on Wednesday, also is being introduced to catching. Moore will be working some with catching coach Brian Schneider, and he may wind up as the emergency catcher.
Joe Frisaro has covered the Marlins for MLB.com since 2002. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.