Replacement: Mike Adams, 4.7 K/BB rate
Some people might even consider Mike Adams to be the better pitcher between him and Bell. The bottom line is that you want to add Adams now as Bell is extremely likely to be dealt. There have been rumors that Adams himself could be dealt, but the Padres would have to be blown away to make such a move.
Replacement: Tyler Clippard, 3.8 K/BB rate
Based on strikeout and walk numbers, Clippard has been the more dominant pitcher when compared to Storen. The Nats are said to be shopping all relievers, but I bet they're secretly hoping to get a big return for their young closer. Storen is young, under team control and has 24 saves on the year. He also has a below average 6.7 K/9 this season. That's not to say that Storen can't develop into a more dominant reliever in the future, but the Nats may realize that replacing his production will be an easier task than at most other positions. If Clippard gets the role, he'd be a solid #2 fantasy closer.
Replacement: Edward Mujica, 6.2 K/BB rate
The consensus seems to be that Mike Dunn would take over closer duties should Nunez be traded. However, I'd put my money on Edward Mujica or Steve Cishek. Dunn has the big fastball, but he also has two factors working against him: His command is sub-par (5.4 BB/9) and he's a lefty. Managers tend to favor right-handed relievers in the closer's role and use their lefties earlier in the game for a left-on-left matchup. Both Mujica and Cishek have much better control than Dunn and both are right-handed. If Nunez is dealt, it may become a closer-by-committee, but I'll give Mujica the edge in save opps. Trader Jack might favor Mujica's experience over the younger Cishek.
Replacement: Matt Lindstrom, 2.6 K/BB rate
The Rockies still have a chance to contend, but they might be looking to trade away some of their bullpen depth, contenders or not. Street has the save numbers, which some teams still value. Lindstrom would likely take over closer duties as he has "experience" in the role and has performed well this season in a set-up role.
Remplacement: Grant Balfour, 2.8 K/BB rate
Brian Fuentes may have the saves under his belt, but he's not nearly as effective a reliever as Balfour is. The A's love to build up closers and flip them for prospects. They could very well do the same with Balfour for the rest of this season and into next.
Potential closers ranked:
1. Mike Adams
2. Tyler Clippard
3. Grant Balfour
4. Matt Lindstrom
5. Edward Mujica