The 28 year old and former first round pick by the Astros is looking to return to all star form in his walk year. Castro's 2013 campaign included 120 games (98 behind the plate) and the rest as the designated hitter. He had a slash line of .276/.356/.485 good enough for an .835 OPS. He also had an OPS+ of 130 while walking 50 times and striking out 130 times for the 2013 campaign. He also had 54 extra base hits within his 120 hits good for almost a 50% extra base hit percentage.
The Astros recently won their case with Castro in Arbitration where Castro will be awarded five million for the 2016 season. It's a prove it year for Castro similar to Colby Rasmus last year as he's struggled since the 2013 campaign as his average, on-base percentage, slugging percentage and OPS have steadily went down since the 2013 season. Here's an excerpt via brooksbaseball.net: "In 2015 Against Fastballs (956 seen), he had an aggressive approach at the plate (-0.08 c) with a disastrously high likelihood to swing and miss (32% whiff/swing). When he connected (102 tracked), he generated average power (90.5 mph average exit velocity) and has slight pull tendencies (6° average spray angle)."
The fastballs account for 62% of the pitches he saw and his aggressive approach with high swing and miss rate led to 115 strikeouts in 375 at bats. If he can shorten his swing a bit and improve on his pitch recognition I could see an increase in average by 25 to 30 points to around a .245 to .255 average. His power is definitely there with 30 extra base hits last year in only 100 games. Surprisingly there hasn't been much pull in his swing which gives me hope of the average improving this year and the numbers to improve with more steady playing time. The Astros backup last season Hank Conger moved on to the Rays in free agency this season. Conger caught 69 games and provided similar numbers to Castro with 22 extra base hits and a .311 on-base percentage.
Castro will be the starter as his main competition Conger mentioned above is not with the team. On the depth charts via MLB.com Max Stassi is listed as the backup. Stassi a fourth round pick of the Oakland Athletics in 2009 played in 11 games last season and 10 we're behind the plate. In my initial thought I see Castro catching anywhere between 105-120 games barring injury and Stassi catching the rest of the games.
It's going to be an interesting season as since Stassi doesn't have much MLB experience the Astros will lean on Castro even more this year. As mentioned above Rasmus did fairly well in this pending free agency route last year that led to him receiving a qualifying offer. Castro is hoping for a strong campaign in 2016 that would lead to a multiyear deal in free agency.