Earlier this week, Tito indicated that a couple more players would be brought up in the next few days, and this afternoon those players were announced:
Indians 40 is full so 2 need bumped for Soto/Martinez. Moncrief seems likely. Other options: Aquino, Choice, Merritt, Wolters, Holt, Aguilar
— August Fagerstrom (@AugustF_MLB) September 3, 2015
The 32yo Martinez is pretty much "Aviles-lite" (yes, hardly a rininging endorsement), a versatile fielder with a bat that simply hasn't translated to the MLB (.181/.231/.251 in 403 career ABs). Martinez has earned his spot having been a cornerstone of the Clippers' playoff bound team this year, featuring in 102 games with an excellent .289/.344/.424 line (123 wRC+). The majority of those games were at 2B, but he has also started 12 games at SS and 16 at CF. However, he is similar to Almonte in that he is a switch-hitter who is much more effective when facing RHP, so they can't simply be platooned in CF. I suspect that (barring some key injuries) Martinez will mainly be used in a pinch-runner/late defensive replacement role.
The lefty reliever Giovanni Soto is much the more intriguing of these promotions. Originally drafted by the Tigers in the 21st rd in 2009, Soto was acquired by the Indians in the Jhonny Peralta trade midway through 2010. After a solid season starting in Akron in 2012, he made it to Columbus at age 22 in 2013, but then suffered a back injury that sidelined him for nearly the whole season.
After a solid comeback year as a reliever in Akron, Soto spent last winter in Caribbean, where he was initially a reliever in the Puerto Rican Winter League, before being switched to a starting role. Suddenly everything seemed to click and he finished with a PWL ERA of 2.20 (9.0 K/9) over 45 IP.
Reverting to a reliever role this season at Columbus, Soto was lights-out early on, but then went through a two-month slump from early June to early August before returning to form with 8.2 scoreless innings since Aug 8th. Although his ERA doesn't really reflect it, Soto is more than just a LOOGY, as he has done a good job preventing solid contact against righties as well.
The Tribe hasn't yet announced who will be moved to make room for Martinez and Soto, neither of whom is on the 40-man. As Todd Paquette pointed out, one possibility is simply to move TJ House from the 15-day DL to the 60-day DL, since it doesn't look like he will be returning this year. Of the other possibilities mentioned by Fagerstromin his Tweet, I would agree with him that Carlos Moncrief (who was demoted from AAA to AA in mid-season) is the most probable candidate.