They are promoting infield prospect Wilmer Difo to the major league team. Difo, 23, has played at both High-A and Double-A this season for a combined 33 games and 127 at-bats. In those 33 games, Difo has hit .315 with a .367 on-base percentage.
Rosenthal mentions in his tweet that Jayson Werth is candidate for this disabled list. Werth was hit by a pitch last Friday in San Diego and an MRI on his left wrist showed no broken bones or torn ligaments.
Difo has played both shortstop and second base throughout his minor league career. Back in December, Difo was rated the 7th best prospect in the Nationals system by Baseball America.
The big question coming from this move is where Difo will play during his promotion. As mentioned above, he has played both short and second base in his career. In 389 minor league games, Difo has played 282 of them at shortstop and 94 at second base with 13 other games at third.
Playing shortstop with the big league club may be an issue because the Nationals have Ian Desmond already there. Desmond is off to a pretty brutal start in 2015, hitting .239 with only two home runs in 39 games. Those numbers don't include the bad start he got off to defensively. In 154 games last season, Desmond made 24 errors. He has already made 11 in 39 games this season. This year is a far cry from Desmond's normal offensive output, as he has hit for 20-plus home runs in each of the past three seasons.
Difo could also go play second base, where Danny Espinosa is currently playing. Espinosa is hitting the ball well though, at .275 with a .373 on-base percentage to go with five home runs in 31 games.
Difo will likely come off the bench, providing some infield depth and speed on a short-term basis while a roster spot is available. Because he only has 33 games above Low-A for his career, the move is not likely to be a long-term one and Difo is expected to return to the minors to continue his development in the near future.