That new catcher replacing Tyler Flowers is Dioner Navarro.
Which really means that the catcher replacing Flowers is Alex Avila, who is now going to be catching a lot more often that I would have originally estimated, because this combination only makes sense as a strict platoon where Avila is the primary guy and Navarro mashes lefties.
Statistically, there's some basis for this. Navarro owns a career 110 wRC+ vs. lefties, and Avila is even better vs. righties at 116 wRC+ against righties. If they can both be average or above against opposite-handed hitters, the Sox have squeezed more offense out of the position, even above-average offense, for likely under $5 million.
Of course, they wouldn't be able to do this if either guy was coming off a strong or particularly encouraging campaign. Avila, 28, looked worn out in 2015 while being limited to 67 games due to injury and posted career-worst rates in power and batting average, while being pushed out of a long-held job by the previously unheralded James McCann, and he's the younger guy here.
Navarro, 31, posted a burly .894 OPS vs. lefties last year, but in just 36 PA, as he was buried by Russell Martin. The two of them combined covered barely 400 PAs in 2015, and now have the whole catcher position to themselves. Navarro did well enough as a starter in 2014, but there's a risk in trying to get full-time work from two guys you'd rather not see shoved into the daily grind on their own.
This is also an offense-only perspective, which is what you have to have to be really happy with this move. Tyler Flowers' enormous frame wasn't much for blocking pitches, but his rapport with Chris Sale was regularly lauded, and Carlos Rodon's 2015 season turned around after they were paired together. I hope you're skeptical of pitch-framing as an innate skill rather than something that can be taught, because the Sox just ditched a top-10 guy in the league for a platoon of backstops who rate below-average.
This platoon is a plan. A cheap one with significant risk, but one with some reasoning about it, and it's cheapness washes away some of the concern that they wasted effort to fix a catching situation that wasn't nearly as urgent as third base and shortstop right now. If it's just part of a larger offseason campaign full of aggressive fixes to the offense, it looks creative and crafty. If it's part of a thrifty free agency period that still ends with 500+ PAs for Tyler Saladino and Avisail Garcia, it looks like pointless one-year noodling that served to do little more than probably piss off the most talented pitcher in franchise history.