It's just a minor-league deal with an invite to spring training, and given the log-jam ahead of him, hard to imagine many scenarios in which he makes the Opening Day roster - except for ones involving the team bus and the I-10 stack. Weeks's last truly productive season was 2011, when he made the All-Star game with the Brewers at Chase Field. You may recall some furore because Prince Fielder picked him over Justin Upton for the Home Run Derby: I was there in person to boo Weeks lustily - along with most of the home fans - for his lame showing. So, kinda ironic he is now one of us.
Since then, Weeks' career has gone downhill sharpish. He actually hit pretty well in 2014, putting up a 123 OPS+ in his last season with Milwaukee, but defensive indifference reduced his overall value to 0.2 bWAR. He left the Brewers last season for Seattle, putting up a line of .167/.263/.250 over 37 games with the Mariners, before being DFA'd and subsequently released. He's 33 now, and unless he can suddenly turn around and bat left-handed, this seems like purely an addition for reasons of depth. Interesting to note he played the outfield in Seattle, starting ten games in left field.
Steve Gilbert was the first to announce the news:
#Dbacks signed Rickie Weeks to a Minor League contract with an invitation to Major League Spring Training.— Steve Gilbert (@SteveGilbertMLB) February 27, 2016