He's now joined the team. There s been no official announcement from the Cubs, but Rivera is in Sunday's lineup:
And thus, he must be on the active roster.
Rivera has a reputation as an excellent pitch-framer and catcher of base-stealers; he’s thrown out 36 percent of attempts against him this year (12 of 33), and had a 30 percent CS rate in 2016 (18 of 61) and 37 percent in 2015 (23 of 63). His career rate is 36 percent.
So that’ll be helpful to the Cubs defensively as they await the return of Willson Contreras, which is still a few weeks away.
Though Rivera isn’t a good hitter overall, he still hits lefthanders pretty well. This year in a small sample size, he’s hitting .250/.268/.575 (10-for-40) with four home runs. So I suspect we’ll see him start quite a number of games vs. LH starters until Contreras comes back.
Again, there has been no official word, but the only logical 25-man roster move would be to return Victor Caratini to Triple-A Iowa as a result of Rivera’s activation. Caratini had a nice 3-for-3 day Friday against the Blue Jays, and eventually he’ll be a good major-league hitter. He’ll certainly be back in a week and a half when rosters expand.
To make room for Rivera on the 40-man roster after he was acquired Saturday, Aaron Brooks was designated for assignment. Brooks, who was acquired from the Athletics for Chris Coghlan last year, spent most of 2016 on the DL and hasn’t really been any good this year, either. I suspect he’ll wind up released, but if the Cubs can get even an A-ball lottery ticket for him, that’d be all right.
UPDATE: The roster move is now official: