The Nationals gave up four good prospects to add Gio Gonzalez to their rotation, and now Washington has signed the left-handed starter to a contract extension that could keep him in a Nats uniform through 2018.

Gonzalez agreed to a five-year, $42 million contract three weeks after arriving in Washington. He made $420,000 last season and is likely a very happy person right now. The contract buys out one year of free agency, and includes 2017 and 2018 club options.

Washington acquired Gonzalez from the Athletics in exchange for a package of four prospects: A.J. Cole, Brad Peacock, Derek Norris, and Tommy Milone.

In 2011, Gonzalez went 16-12 with a 3.12 ERA in 32 starts and 202 innings pitched and represented the A's in the All-Star game. He will join Stephen Strasburg and Jordan Zimmerman atop what's rounding into a fine little rotation in Washington.

Gonzalez has already made himself home within the Washington organization. He's starting pitcher and assistant GM:

Now that we are in the Nations Capital, we need a Prince. Come on Fielder!

— Gio Gonzalez (@GioGonzalez47) December 24, 2011

For the latest Nationals news and fan perspective, visit Federal Baseball and SB Nation DC.