Webb posted a 2.91 ERA in 59 IP with the padres last year. A closer look at peripherals (1.41 WHIP, 6.71 K/9) and his home/ road ERAs (0.90/4.97) suggest that he probably can't be counted on to match his ERA next year.
Mujica pitched 69.2 innings for the Padres, striking out 9.30/9 and allowing just 6 walks. He did give up 14 HRs though, and also had a Petco-favorable split (2.67/4.35).
Maybin struggled in the majors, but was solid in AAA again.
I like this deal for San Diego, as any time you get can get young toolsy OF with upside for a couple of solid if unspectacular relievers, you do it. What's everyone else think?