The 29-year-old, 2007 Toronto 16th Round draft pick out of Mount Kisco, New York, has played a total of 129 major league games between the Blue Jays and Minnesota Twins who selected him off waivers from the Jays in February of 2012.
The Jays then selected Mastroianni off waivers from the Twins in April of 2014, but he was granted free agency after the 2014 campaign and he signed as a free agent with the Phillies.
In his 129 games and 306 plate appearances in the majors, the right-handed hitting and throwing, 5'11'', 190 lb outfielder has put a .212/.274/.289 line with five doubles, two triples and four home runs in 306 plate appearances.
Over nine minor league seasons, Mastroianni has posted a combined .279/.367/.370 line.
At Triple-A in the Twins and Blue Jays' system in 2014, he put up a .277/.354/.379 line with 20 doubles, a triple and five home runs in 92 games and 413 plate appearances, and posted a combined .116/.136/.186 line in 21 games and 44 PAs with the Jays and Twins last season.
In 16 games and 64 PAs at Triple-A Lehigh Valley in the Phillies' system this season, Mastroianni had a .293/.333/.362 line with four doubles before today's trade.
With the news that Reed Johnson underwent surgery on his foot yesterday and will likely be out for most if not all of the season, and Michael Taylor currently in the majors, the Triple-A Syracuse Chiefs were left with just four outfielders on their roster, so the trade gives the Nationals some organizational depth.