Olson last played for the Kansas City Phantoms in the Champions Indoor Football League.
"He's a great guy. He's a guy right now that's being talked about," Harbaugh said of Kaepernick, per Conor Orr of NFL.com. "We'll just see what happens with that. Only speculation right now. He's a really good football player and like I said, I do believe he'll be playing in the National Football League this year."
Amy Trask of CBS Sports also provided her impression of owner Steve Bisciotti's thoughts on the issue:
The Olson signing comes after Rapoport reported Wednesday that Ravens quarterback Joe Flacco could miss up to three-to-six weeks with a disc issue in his back.
Ryan Mallett and Dustin Vaughn are the only other quarterbacks on the roster and combined for just six pass attempts last season.
Meanwhile, Olson has even less high-level experience after throwing just three passes in his entire college career. He finished 1-of-3 for minus-1 yards at Clemson after transferring from Stanford.
Presumably, former Stanford coach Jim Harbaugh tipped off his brother, John, about his former player.
Still, Kaepernick remains unsigned despite posting a 90.7 quarterback rating in 12 games last season with 16 touchdowns and four interceptions.