Guillon (personal) arrived at Nationals camp Thursday, Jorge Castillo of The Washington Post reports.

Guillon has not reported to spring camp due to difficulties with his visa, Mark Zuckerman of MASN Sports reports.

Reds prospect LHP Ismael Guillon allowed two earned runs with nine strikeouts in seven innings on Sunday for Low-A Dayton. He allowed four hits and walked one batter in the outing. The 22-year-old southpaw has made strides this season in his second tour of the Midwest League, registering a 2.79 ERA and 67-24 strikeout-to-walk ratio in 61 1/3 innings. Meanwhile, Guillon's outstanding changeup, which is widely considered to be one of the best in the minor leagues, has helped him strike out right-handed batters at a 29.5% clip while holding them to a .160 batting average.

Reds left-handed prospect Ismael Guillon fanned 11 batters in seven shutout innings on Wednesday for Low-A Dayton. Guillon is in the Midwest League for the third consecutive season. There were indications that the Reds were going to promote him to Double-A Pensacola to start the season, but he ended up back in Dayton. Guillon should see a promotion soon, though it could be to High-A Bakersfield and not Double-A. He sports a 1.16 ERA and 9.6 K/9 for the season, so it will be interesting to see if he can maintain his level of success in the event of a promotion.

Reds optioned LHP Ismael Guillon to Double-A Pensacola. Guillon was knocked around for six runs over 4 2/3 innings this spring. The 22-year-old will get his first try at Double-A this season.