It's long been said that momentum is tomorrow's starting pitcher, but maybe that old saw misses the point.

Of baseball's 10 best starting staffs in 2010 (measured by ERA), exactly three made the playoffs. Meanwhile, six of the top eight bullpens could be found on postseason teams. Maybe momentum is really tomorrow's relievers.

Relief pitching -- and more specifically, middle and setup relief -- has never been more important in baseball than it is right now. Even top starters rarely finish games. Meanwhile, elite closers are almost never asked to get even four outs.

In between, games are won and lost every day. Teams that have a bullpen that can turn a sixth-inning lead into a ninth-inning save opportunity are teams that win games.

"The most devastating part of a team is when a team loses late on a consistent basis," Rays manager Joe Maddon said. "When you have games won in the seventh and eighth, and you're losing a lot of eighth- and ninth-inning games, the tone in the clubhouse at that time is where it can really go south."

The question is how to go about making those leads stand up. It has become clear this offseason that relievers are once again taking their skills to the bank. Joaquin Benoit got three years from the Tigers, and the Angels gave three years to Scott Downs. The Dodgers have reportedly inked longtime Twins right-hander Matt Guerrier to a three-year deal. Recent history seems to indicate, though, that that's not the best way to build a bullpen.

The strategy is correct: Fill your 'pen with as many big-time arms as possible, not just a star in the ninth inning. The tactics may be questionable. Guaranteeing multiple years to a veteran relief pitcher is a risky proposition -- something even Tigers GM Dave Dombrowski acknowledged when he discussed the Benoit deal.

"I understand all the controversy that's attached to signing a reliever for three years compared to two," Dombrowski said. "We've done all the research. We've got all the statistics. We've got all those things. But for us, we thought he was a very good signing, a guy that we liked a lot."

Whether the increasing specialization in relief pitching is a cause or a consequence of starting pitchers going fewer innings, it's pretty clearly here to stay. Twelve- and even 13-man pitching staffs rule the day, with two or three lefties, designated seventh- and eighth-inning right-handers.

And the truth is, not all seven or eight relievers need to be studs. That's just about impossible, frankly. But a good club does need more than one or two quality relievers at the back end of the bullpen. The best relief corps have several. Witness the Angels in recent years, or the gold standards in '10, the Giants and the Padres.

Then look at how those staffs were built. In San Francisco, Brian Wilson and Sergio Romo were homegrown. Santiago Casilla and Guillermo Mota were essentially scrap-heap signings, each getting a one-year deal. Only Jeremy Affeldt was acquired with a multiyear, free-agent contract. Likewise in San Diego, where not a single one of the top-five relievers was signed as a free agent.

The Cardinals have had success in recent years with low-dollar relievers all over, including in the ninth inning. There's a certain irony here, that as teams are really coming to understand the essential nature of having quality bullpen depth, they're also learning the risks in trying to acquire it externally.

In St. Louis' case, the club has built a 'pen where the three key setup/middle right-handers are two converted starters and a converted catcher.

"Developing starters -- that's a good thing," said Cards general manager John Mozeliak. "You can always go the other way."

The paradox is that while building a bullpen is absolutely essential, it's also very easy to do wrong. Whereas overall payroll can be a useful guide in guessing a team's future success, that does not apply in the bullpen. For an example, look no further than the '10 Phillies, who had a very expensive and only mildly effective bullpen.

It's not that the Phillies' relief corps was awful. But it certainly wasn't good enough. And, perhaps, if they hadn't spent a combined $25.7 million on Brad Lidge, Ryan Madson, J.C. Romero, Chad Durbin and Danys Baez, they might not have had to make that choice between Cliff Lee and Roy Halladay in the first place.

This is not to say that clubs should never spend on relief pitching. As with so many areas of life, it's a matter of what you choose to spend on. Mariano Rivera continues to be a great investment for the Yankees. A certain few relievers are so dependable and so good that it's worth it. But many others are extremely inconsistent from year to year.

That, of course, is part of why it's so important to have a slew of big arms. If your projected eighth-inning guy struggles, you need someone to step in and do that job. Depth is absolutely essential.

The Tigers know that. The Angels know that. So do the Giants and Padres. They're all doing it in different ways, but they're all trying to accomplish the same thing.