Bradley and Jungmann shouldn't come as much of a surprise. The Brewers two first round picks in 2011 had no real chance of making the roster. While some draft picks move quickly through systems, neither player has pitched above High A-Ball yet. Bradley performed better than Jungmann in his brief Major League Spring Training stint, striking out six batters and walking just one over 4.2 innings. Jungmann gave up three walks and struck out one in 2.2 innings.
Leon is similarly unsurprising, though he's had a bit more time in the minors than Jungmann and Bradley. Leon has never been particularly great in his minor league career, however, and similarly struggled in spring ball thus far with two earned runs and two walks in 1.2 innings.
Byrd is a little more curious, as he may have had an outside shot at a bullpen spot this spring. He has been very effective in Double-A the past two years, with a sub 3.00 ERA both seasons. He also posted a career high 8.8 K/9 in 2012. He pitched in just one game for the Brewers during spring training this year, recording just one out while walking three batters. He is likely ticketed for Triple-A. If he continues to pitch well there, he could see a call-up sometime during the year.
In addition to these moves, Ariel Pena, Santo Manzanillo, Miguel De Los Santos were all optioned to Double-A Huntsville today. None of them have been able to truly impress throughout their careers, though De Los Santos's career 13.6 K/9 is certainly appetizing.