Heading into Spring Training, the top four spots in the rotation are filled by Scott Kazmir, Casey Fossum, Jae Seo and James Shields. Ryu will compete for the fifth spot against: J.P. Howell, Jason Hammel, Edwin Jackson, Brian Stokes, Mitch Talbot and Jeff Niemann.
"We'll take a look at [Ryu] in the bullpen, too," Friedman said. "We're going to keep an open mind."
To clear room on the 40-man roster, the Rays designated right-hander Marcos Carvajal for assignment.
Ryu hails from Choon Chung Do, South Korea. The 23-year-old made his Major League debut with the Cubs in 2006, posting an 0-1 record and an 8.40 ERA in 10 games (one start) over four stints with the club. He struck out 17 in 15 innings. He also pitched in 24 games (23 starts) with Triple-A Iowa, and he went 8-8 with a 3.23 ERA, the sixth-best ERA in the Pacific Coast League.
In 2005, Ryu pitched for Double-A West Tennessee and led the league with 169 2/3 innings in 27 starts, while compiling an 11-8 record and a 3.34 ERA. In 94 career Minor League outings (72 starts), he has gone 28-20 with a 3.48 ERA, striking out 385 in 437 innings.
Ryu joins Seo, a fellow South Korea native and right-hander, on the Rays roster.
Lopez batted .256 in 56 games with the Rookie-level Princeton Rays in 2006, leading the team with three triples. The 20-year-old was originally selected by the Rays in the eighth round of the 2005 First-Year Player Draft.
Reinhard made 26 starts for the Class A Southwest Michigan Devil Rays, working to a 6-10 record with a 4.50 ERA. His 134 strikeouts were fifth-most among Rays Minor Leaguers. The 23-year-old was selected by the Rays in the sixth round of the 2005 draft.
Carvajal appeared in 39 games out of the bullpen with the Double-A Montgomery, going 2-2 with a 3.86 ERA while holding opponents to a staff-best .239 batting average. The 22-year-old was acquired by the Rays on April 6, 2006, from the Mariners in exchange for Minor League right-hander Jose De La Cruz. The Rays have 10 days to trade, release or ask waivers on him.