Rosenthal has been brutal lately, so this isn't shocking news. He blew the save last night, and has allowed 11 runs in seven June innings with eight walks and 13 hits. Matheny will likely turn to Seung-hwan Oh to replace Rosenthal. Oh has been hailed as the Mariano Rivera of Korea, and has been excellent in his 38 innings with the Cardinals this season, with a 12.08 ERA, 1.89 BB/9, and sparkling 1.66 ERA. If you really want to hedge your bets you can also roster Kevin Siegrist who has also been quite good this season (2.79 ERA, 9.9 K/9) but is a lefty. If Oh does indeed inherit the closer's role, he may not relinquish it.
He's still recovering from elbow surgery, but this is exciting news. He'll still need some seasoning in the minors before he joins the Major League club, but could be with the White Sox sometime after the All-Star Break. His .300+ averages from his time with the Rockies aren't likely to recur since he won't have the bonus of playing half his games in Coors Field, but there's a chance he will be effective enough to be a corner infield option in deeper mixed leagues once he's in game shape.
Smoak hasn't played since Wednesday as he continues to nurse a left knee injury. There aren't many that are counting on his production as it is; he doesn't receive consistent playing time, and a 30.1% K% has contributed to his lackluster .243 average. He has dramatically increased his walk rate to 12.9%, up 4.1% from his 2015 mark of 8.8%, and that at least puts him in play in daily OBP leagues.
It's not exactly an embarrassment of riches for the Padres as their rotation would consist of Cashner, Drew Pomeranz, Luis Perdomo, Colin Rea, Christian Friedrich, and Erik Johnson. Rather than simply a move to keep those names in the rotation, it's a strategic move to help limit the workload of many of the Padres young starters heading into the All-Star Break. Pomeranz is the only real fantasy relevant one of the bunch, although Cashner does carry some semblance of upside that he flashed in prior seasons.