When the Tigers signed Joe Nathan in the offseason, it appeared as thought they had locked down the ninth inning with one of the best veteran relievers in the game. Nathan was coming off of a fantastic two-year stretch with the Rangers in which he saved 80 games and posted a 2.09 ERA in one of the most hitter-firendly parks in the game.
The club also added Joba Chamberlain in free agency and traded for Ian Krol -- in the Doug Fister trade that may or may not have been an effort to clear space in their budget for Nathan. Krol has been the club's best reliever based on ERA alone, but as a whole, the Tigers' bullpen has been awful -- especially Joe Nathan and Phil Coke.
General manager Dave Dombrowski doesn't make mistakes often, so if he begins to scour the trade market looking to improve his club's biggest weakness, the Tigers could find themselves in a much better position to compete for the rest of the season and in the playoffs.
The Diamondbacks could push their way back into the Wild Card race, if you can believe that. It seems like they've been on the outside looking in since their Opening Day loss to the Dodgers in Australia. However, they're just five-a-half games back of the Dodgers and other Wild Card contenders. It won't be easy, but they could get back into the mix.
If they don't, veterans on expiring contracts could be dealt with the future in mind. Brad Ziegler, who is sporting a 2.70 ERA this season, has been one of the most consistent relievers in baseball over the last five years or so. He's almost always among the league leaders in groundball percentage and he rarely hands out free bases. He'll be a free agent after the season, and Arizona definitely won't extend him a qualifying offer. Trading him in July might be the only way for them to guarantee a return on his production.
Juan Carlos Oviedo
The Rays are the worst team in baseball right now. Part of the reason for that has been a direct result of their reliever renaissance magic running out. Grant Balfour and Heath Bell have been busts, but Juan Carlos Oviedo has been surprisingly productive. He's been the club's most valuable reliever despite walking more than four batter per nine innings. That could catch up to him, but for now, he's in a groove, posting a 2.25 ERA in 20 innings pitched.
Hector Rondon, Wesley Wright
The Cubs might want to hold on to Rondon for their inevitable trek into genuine contention. He's just 26 years old and he's been excellent this season, putting together a 2.45 ERA and a 1.75 FIP in over 25 innings this season. He could command more than the Tigers would like to give up for a guy that will only pitch an inning at a time.
Wright, on the other hand, could be a useful lefty in Detroit if the team moves on from the struggling Phil Coke. He has a 2.40 Era in 19 innings so far, and was considerably productive for the Astros and Cubs last season. He's pushing 30, so he isn't likely to cost an acquiring team a top prospect.
Jonathan Papelbon, Mike Adams
There's almost no way anyone will acquire Papelbon. The Phillies would likely have to eat a significant portion of his contract and it'd be hard for them to get anything worthwhile in return. If they're going to pay him, they might as well put him to work. He's having a strong year -- 1.54 ERA and 13 saves -- but he's put up a career-low strikeout rate and his velocity has dropped every year since he signed with Philadelphia. He will earn $13 million in 2014 and 2015 and his contract includes a $13 million vesting option for 2016. He could probably help the Tigers, but bringing him to Detroit might be more trouble than it's worth.
Mike Adams will be a free agent after the season unless he appears in 46 more games for Philly. That's unlikely. He's been effective so far this year with a 2.12 ERA in 17 innings. Three months of Adams wouldn't likely cost the Tigers a significant prospect.
Street will hit the open market after the season as well. Unless the Padres are in a strong position to contend for the postseason, they could decide to ship Street to Detroit or another club for a player that might help them in the future. He has 18 saves and a 1.08 ERA this year. A move to Comerica Park could hurt his numbers a bit, since Petco is such a pitching haven, but even if the change of scenery caused him to add two full runs to his ERA, he'd still be the best reliever in Detroit.