a.k.a. K-Rod/Frankie Rodriguez is a bit removed from his stretch as one of the more dominating relievers in the game but is definitely still useful in the bullpen and could fill in as a closer somewhere (like he did for the Brewers when Jim Henderson missed some time due to injury). During his time with the Brewers, he's been up and down (2011 & 2013 he pitched well while 2012 was primarily a season to forget and he could be in a Brewer uniform soon as they have been one (of quite a few teams) tied to speculation on where he may sign (though his days of making north of $10 million a year are likely done). He's one of those players that he's been in the bigs long enough that you forget that he's not that old (32).
Through his age 31 season, the most similar player to him was Armando Benitez. After that age (when he was coming off his best season, he pitched four more seasons with only one of them being above average). I think that whoever gets K-Rod should get some decent production and should be an okay deal as long as they don't overpay due to past status of being a star.
Williams has had an interesting career. He started off somewhat promising for a few years before injury & ineffectiveness led him to the minors and even some independent league ball for a few years before coming back as an inning-eater (but not particularly effective starting pitcher). I think he'll end up somewhere having to compete for a #5 rotation spot and get some innings but not will likely have to get his ERA+ above 82/83 mark of the last couple seasons to keep whatever job he gets for the entire season.
His most similar player through age 31 is Bob Milacki who's career was finished after his age 31 season and 7 ineffective games for the 1996 Mariners. It seems as though Milacki's career does live on through whatifsports.com as his 1988 season is one several teams for their Sim League Baseball.
If you would have told me that Tommy Hanson's career was in danger of being washed out by age 27 when he was a rookie, I would have thought you were crazy as Hanson had a very strong rookie season in 2009 and followed that up with a couple above average seasons. However, his ERA+ has decreased every year since he was a rookie, cratering at 70 last year and falling out of favor even in a mediocre Angels rotation.
Still, he has had some success before and someone will take a chance that he can recapture some of his early career success something that seemed to not happen for his most similar player through age 27 (Wade Miller) who had a couple decent partial seasons and pitched his last game at age 30.
One of the last remaining of ex-Montreal Expos players is still available. Ayala has drifted from team to team over the last few years and has pitched relatively well where ever he has gone. Signing him is not going to make major headlines but he looks to be a useful bullpen piece for teams hoping to contend (he's played in the post season the last three years, all with different teams, 2011 Yankees, 2012 Orioles, 2013 Braves).
History indicates he may have a few more years ahead of him. His top comparison through age 35 is Steve Reed who had four above average seasons going from bullpen to bullpen once he reached his late 30's.