Per Twitter. And the radio, obviously.
WFAA's Or Moyal has a good Q&A up with Scout.com's Jason Cole this morning that takes a detailed look at some of the players the Rangers could be looking at recalling to the majors, and Hamburger was prominently featured in that discussion:
Mark Hamburger is a lesser-known arm whose main claim to fame is a great last name. What kind of pitcher is he? Are his recent starts reflective of a different view on his role, or are the Rangers committed to using him in the bullpen?
The last question is a good one, and I don't really know the answer. Hamburger had never started a game in his professional career until recently, but the results as a starter have been excellent––16.1 innings, 9 hits, 2 runs, 3 walks, 14 strikeouts. He is succeeding and keeping manageable pitch counts because he does a good job of commanding a 90-96 mph fastball, which has some late life to it.
I still think Hamburger is likely a reliever because his secondary stuff lags behind the fastball. His slider has improved this season, though, as he's now throwing it in the upper-80s with a little more late bite. He is also mixing in a splitter. Most of Hamburger's success as a starting pitcher has come from his ability to command a plus fastball, though.
Hamburger may not project as a late-inning reliever because he doesn't really have a swing-and-miss secondary pitch, but he is beginning to look more and more like a big league-caliber arm that could pitch in middle relief.
Martin, meanwhile, has scuffled at the plate during his stint at Triple-A Round Rock, hitting just .263/.316/.314 with no home runs in 40 games, and Cole speculates in the piece that a promotion for Martin would be more about acclimating him to the major league environment for the first time than actually starting him down the stretch in meaningful games. It's unclear how the potential seriousness of the Cruz injury could end up mucking things up in that regard, but with Hamilton, Chavez, Gentry, and Murphy still available, I would suspect that Martin's usage will largely be restricted to pinch-running duties and some late-game substitutions in games that are out of hand one way or the other.
And, hell, maybe he can catch some lightning in a bottle and put some of that $15.5 million talent on display over an extended period of time. Sans the questions about the bat, Martin is a premium defensive talent who can play a legitimate center field, and who is still regarded as the Rangers' center fielder of the future.