After the signings of Masahiro Tanaka and Matt Garza, several other teams could become involved. Cotillo lists the Diamondbacks, Tigers, Royals, and Blue Jays as teams that could begin to show more serious interest, but notes that it's "still early" in the process .
The Yankees and Mariners have been rumored to be more interested in adding supplemental pieces at the moment, but given their early offseason spending habits, it's hard to count either club out. The Rockies and Blue Jays could sign Santana without surrendering a first-round draft choice since their picks are protected. Cotillo mentions the Blue Jays specifically, saying they could be waiting for Santana's price to come down before making a serious offer.
The Dodgers and Orioles have consistently appeared in rumors surrounding the market for starting pitchers, and both clubs might be willing to part with their first-round picks for the right free agent. However, the Dodgers already have several options, and have placed an emphasis on maintaining a strong farm despite their extravagant spending. The Orioles have been linked Ubaldo Jimenez as well.
Although Arizona could consider signing Santana, they could also decide to move forward with what they have after their Plan A -- Masahiro Tanaka -- didn't pan out. Cotillo also mentions the Tigers and Cubs in his report, but neither team seems likely to give up a pick at this point.
The Royals could re-enter the chase for Santana as well. They currently have free agent addition Jason Vargas slotted into the number two spot in their rotation, and Santana was exceptionally valuable to them last year. They would effectively be surrendering a draft pick to sign him as well, since they stand to gain a pick at the end of the first round if he signs elsewhere.