Rays manager Joe Maddon said his plans to fill those spots would be announced after Friday night's game.
There is a good chance that one, or maybe even two, starters from Triple-A Durham will be called up to join the rotation.
While Fossum's results as a starter have not been too good this season, which is the primary reason for the move, Maddon explained that moving Fossum strengthened their relief corps by giving the Rays a lefty in the bullpen.
"Obviously, I haven't been putting up good numbers, so I wasn't too surprised," Fossum said. "My arm strength hasn't gotten back yet [from left-shoulder surgery in September]. And I've thrown out of the bullpen. And I think I can help the team better right now throwing out of the bullpen than I can starting."
Fossum began his tenure with the Rays as a member of the bullpen in 2005 after coming to the Rays in a trade with the Diamondbacks.
Handicapping the field:
Durham's starting rotation is highly touted and many Rays fans are eagerly awaiting their arrival. Given the fact Shawn Riggans had been the Bulls' catcher prior to joining the Rays, he was asked for a scouting report on Durham's starting staff.
Right-hander Andrew Sonnanstine is the Durham pitcher most feel will get the next call to Tropicana Field.
"Sonnie, he's excellent," Riggans said. "He pounds the zone. His game is either going to go one way or the other. He's either going to dominate you or you're going to pound him because he throws so many strikes. He uses three different arm angles, from up top, three quarters, and low three-quarters. Three pitches from each arm angle, excellent control, he doesn't walk many guys. He's working on coming inside a little more. Down and away is his money pitch, fastball down and away; slider in the same location. The one problem he has is coming inside, sometimes it leaks out over the plate. He can still throw fastballs by guys with his deception."
Right-hander Jeff Niemann was the Rays' top pick in 2005, but has struggled with injuries.
"Neimann is a power guy," Riggans said. "He's got three good pitches, fastball, curveball, and slider; he throws them all for strikes any time. He can dominate a game. He has a big presence on the mound. He's 6-foot-9, seems like he's right on top of you. He's got a good downward angle. And he's a bulldog. He pitches inside, he doesn't mind hitting guys. He doesn't mind brushing guys back. And that opens up all his off-speed stuff. He's got a real sharp 12-6 breaking ball and a real sharp slider. His changeup is a work in process and he's also working on a splitter right now."
Riggans said Mitch Talbot "probably has the most electric stuff" of the pitchers at Durham. But Riggans added that the right-hander, who was acquired in the deal that sent Aubrey Huff to the Astros, is often his own worst enemy.
"Sometimes he gets into his head a little too much, tries to over think a little too much," Riggans said. "But stepping back from that he also has a very, very good idea about what he wants to do."
Riggans said left-hander J.P. Howell is getting his velocity back and has added a cutter, as has right-hander Jason Hammel.
"All those guys down there have the ability to pitch here and to pitch here for a long time," Riggans said.
He added: "But you can't compare pitching to Major Leaguers to Triple-A players. Nothing can prepare you to be ready for the big leagues except the big leagues. I've never been to one Minor League stadium where there are 50,000 people. I've never played against one Minor League team where there's a player like Gary Sheffield in the lineup."
The Rays play the second game of their four-game series with the Royals Saturday night in a 7:10 p.m. ET contest at Tropicana Field. Right-hander Edwin Jackson (0-6, 7.12 ERA) will start for the Rays and left-hander Odalis Perez (2-5, 5.61 ERA) will start for the Royals.