Melvin initially said the change was "just for today," but when asked later if it was definitely just one day, he said, "We'll see."
"[I was] just looking for a way to get both bats in there," Melvin said. "More than anything, I was playing for today, and we'll see how it plays out."
The D-backs have been without an everyday left fielder since Eric Byrnes went on the disabled list two weeks ago with tears in both hamstrings. Chris Burke, Jeff Salazar and Alex Romero have all gotten starts out there, with none seizing the job.
Jackson played left field coming up through the D-backs' system, but was moved to first base during Spring Training in 2005. Aside from a few games, he has been there since. Jackson started one game in left last season, and went out there one other time during the year in a blowout loss to the Marlins during which he also played third. He played left field once in 2005.
"Coming up as an outfielder in the Minor Leagues, it was definitely more comfortable for me out there than it was as an infielder in college," Jackson said. "I'm just going to take it for what it's worth. It's probably going to be a one-day thing ... I don't know, the discussions haven't even been discussed."
Jackson got a quick refresher course in the afternoon, as he took fungoes in left field and tried to gauge balls hit off the wall.
"I feel comfortable out there," he said. "It's kind of like riding a bike. I went out there earlier today and took some flyballs and balls off the wall. I've played it before. It's not entirely new to me, so I don't think it's that big of a deal for me."
Byrnes is not expected to return until after the weekend at the earliest, which could mean more time for Jackson in the outfield.
"I know he's pretty comfortable in left field," Melvin said. "I think just based on the number of games he's played, he's probably more comfortable there, but I don't think it would take long for him to get comfortable in left."