4:53pm: According to John Perrotto of Pirates Report, the Pirates are also interested in Niemann. He says the Bucs also remain interested in Robert Andino and Jeff Baker.
Additionally, Ed Price of AOL Fanhouse says the Rockies have jumped in on Hammel.
11:16am: Tom Krasovic of the San Diego Union-Tribune wrote Saturday regarding the Padres' interest in Rays pitcher Jeff Niemann:
In return, the defending American League champions have inquired about Padres prospects Simon Castro, Wynn Pelzer, Juedy Valdez and Nick Schmidt. The Padres have deemed the price too high. Niemann is out of minor league options, reducing the Rays' trade leverage.
Out of those four Baseball America likes righty Castro the most, ranking him 14th among Padres prospects. Pitchers Pelzer (16) and Schmidt (21) also make their top 30.
Niemann will make a minor league start today, perhaps his last chance to win the fifth starter job. The decision will probably be made today; Jason Hammel appears to be the favorite. UPDATE: Niemann tossed six scoreless innings.