The first words (we've seen) about Buster Posey's injury -- suffered late last night in a terrible home-plate collision -- from Giants in-game reporter Amy Gutierrez:
Unofficial update: #sfgiants Chris Stewart and Brandon Belt called up. Ford to D.L. Posey has broken leg and torn ligaments.
This is essentially as terrible as terrible news gets. Without more details, we can't know how long Posey will be out, but "broken leg" and "torn ligaments" usually mean surgery (or surgeries) and a long recovery process. Last August, Indians catcher Carlos Santana suffered a similar injury and missed the last two months of the season, but two months seems far too low for an estimate of the time Posey will miss. At the moment, it's probably best to assume that Posey will not play again this season.
Which obviously puts a big hole in the Giants' lineup. In the short term, at least, backup backstop Eli Whiteside will get most of the playing time, with 29-year-old Chris Stewart coming up from Triple-A Fresno to spell Whiteside. It won't be a surprise if the Giants look to the trade market for a catcher, though.
Meanwhile, Brandon Belt has fared well in his first taste of AAA, and will now be expected to make up some of the offensive production lost in the absence of Posey.