Which underdog will bark loudest?

Which underdog will bark loudest?

They've got the covers pulled up to their chins but, come April 2, the sleepers will leap out of bed and trigger wake-up calls for the rest of the Major Leagues.

While it may be good advice to let sleeping underdogs lie, the game's favorites know teams dismissed as also-rans are laying in wait out there, ready to wreak havoc with expectations.

This is simply the law of the recent baseball jungle. Teams coming off losing seasons win World Series (2002 Angels, 2003 Marlins), others coming off losing decades play in them (2006 Tigers).

Their ally is momentum, which begets magic, a sudden belief that destiny has joined their side. Hope springs eternal, but there is at least one downtrodden team out there for which the hope will endure through summer and into autumn.

We give you a quintet to watch out for (or, if you're a lead dog, watch your back): Left coast to right, the Diamondbacks, Rockies, Brewers, Indians and Marlins have the potential to pounce.

Just as contenders could be one injury or one painful offseason from disappointment, those on the flip side can be one surprising development from triumph. The line separating the two can be razor thin.

St. Louis manager Tony La Russa even goes so far as to repudiate the very notion of sleepers in today's game -- a term that implies having success where none is expected.

"There are no pushovers," La Russa says. "You come into our camp, you won't find anyone who disrespects any team. Everyone in our division is tough to go up against."

Sounding a similar note about his own division, Tampa Bay skipper Joe Maddon says, "There's a lot of parity. In the American League East, you see really tough pitching every night."

Emphases and star ratings might change, but baseball impact still boils down to pitching. That's where the underdog gets his bite. The Tigers broke through last season because Justin Verlander rocketed to the top and Kenny Rogers unexpectedly stayed there.

Cleveland Indians
After a season of playing possum, the Indians could be the most dangerous in the weeds. They appeared to regress from 93 wins in 2005, to 78, but the step back was really confined to one area.

The offense clicked (870 runs, second in the Majors only to the Yankees) and starting pitching was tough (4.41 ERA, tied for sixth-best in the AL). But the seventh-inning stretch was a Bermuda Triangle that continually swallowed up the Tribe.

Cleveland was the only big-league club that blew nearly as many saves (23) as it converted (24). Which is where Joe Borowski and, setting him up, Roberto Hernandez and Aaron Fultz, come in. All three relievers signed with the Indians as free agents in the offseason.

"Teams that have that bullpen late in the game are the ones that have success," says Casey Blake. "That's what it takes. I think our offense and starting pitching will be tough; everything falls on defense and the bullpen."

Borowski has been in Major League bullpens for a dozen years, but 69 of his career 80 saves have been concentrated into two seasons: 2003, with the Cubs, and last season in Florida. He doesn't strike one as an end-of-bullpen enforcer and, indeed, the Indians weren't sure that's who they were signing to a $4 million contract in early December.

"They were very up front with me," Borowski recalls. "They said, 'Our bullpen was our weakness last year. We need someone in the eighth and ninth innings. If we don't sign anyone else, you'll close, but if we can improve more, we will.'"

Borowski smiles. "That was fine with me, and here we are. I like this team. The offense is very impressive, we got a good starting five. With the additions to the bullpen, we'll be very good."

Florida Marlins
Borowski's last team was surprisingly good. He concurs on what everyone else has been saying about the Marlins, the green club that jelled fast enough last summer to rattle the NL Wild Card race.

"They have a chance to do some very special things," Borowski says. "Hopefully, they'll work as hard as they did last year and keep it going. It's a matter of not getting complacent, thinking you can just throw yourself on the field and do it all the time. As long as they don't sit back on their laurels, they can do it again."

Injuries out of the gate to starter Josh Johnson and Taylor Tankersley, expected to succeed Borowski as the closer, could doom the Marlins to another slow start. But the bliss of youth is that no one is considered irreplaceable.

New manager Fredi Gonzalez concurs, and feels very confident with Sergio Mitre occupying Johnson's spot to join Dontrelle Willis, Scott Olsen, Anibal Sanchez and Ricky Nolasco in the rotation.

"What Joe [Girardi] did there last year was nothing short of fantastic," says Borowski, giving props to the dismissed manager. "He was the perfect manager for that group of guys: he knew when to be hard, and when to console them. But Fredi could be the same, we just don't know yet."

Arizona Diamondbacks
The D-backs could be this season what the Marlins were last -- which can go a long way in the toss-up NL West.

That's the way general manager John Byrnes sizes it up.

"I think our guys will perform, too," Byrnes says. "Enough to give us a chance to win this year."

Even last year, as they were right in the middle of growing young, they were also right in the middle of the race.

Entering August, Arizona was nipping at the heels of the Padres (second place, one game back) and four games up on the eventual Wild Card Dodgers. That experience convinced Byrnes that it was safe to trust the kids, and now the Tot-backs will be out in force.

In one of MLB's most homegrown lineups, only second baseman Orlando Hudson and left fielder Eric Byrnes will be "outsiders." The transition was completed with the midseason arrivals of shortstop Stephen Drew and right fielder Carlos Quentin.

Growing pains? Forget 'em now.

"It's not all about potential," Byrnes says, "but about performance. These guys dominated in the Minors, and Drew, Quentin and [Conor] Jackson showed in the Majors in their first extended playing time that they can play well at this level, too."

The Tot-backs will field an intriguing lineup. There is no focus -- that blurred when Luis Gonzalez got out of the way of the youth movement. There is no one you need to pitch around, but everyone can hurt you.

Still, offense won't carry this team. That's a chore for the pitching staff. Arizona has a reigning Cy Young Award winner (Brandon Webb), but the rotation depends on Randy Johnson getting healthy and Doug Davis getting good again; those two ranked last and third-to-last, respectively, in ERA among AL left-handed starters.

Colorado Rockies
Because it is such a balanced division, the NL West doubles up on sleepers. Now, the Rockies may come off more as a Rip Van Winkle, yet their transition from mere home-bangers to a fundamentally sounder team makes them fascinating.

If that finally was the real Kaz Matsui seen in September, he and Willy Taveras will form a vise atop the lineup. They will squeeze pitchers, and Todd Helton, Garrett Atkins and Matt Holliday (78 homers, 315 RBIs and an average of .319 among them) will finish them off.

Having an 18-game loser (Rodrigo Lopez, lately of the Orioles) as a No. 3 starter makes you a little uneasy. But Aaron Cook and Jeff Francis are solid atop the rotation, and anticipation runs high for rookie Jason Hirsh, a key of the package obtained from Houston for Jason Jennings.

Clint Hurdle will relish managing this team, which will give him more opportunities to be hands-on. His tenure has drawn mixed reviews, but Hurdle has gradually overcome the Rockies' split personality. They now show up on the road. Next step could be showing up the rest of the division.

Milwaukee Brewers
This will also be a steppingstone season in Milwaukee. Only question is, how big will be the step taken by the Brewers, who still have not finished a season with a winning record since 1992.

In a competitive division in which 83 wins were enough last season, the leap from fourth to first can be covered by Ben Sheets. Even during the last two, injury-beset seasons, he has been exceptional when on the mound. But he must find his way there 34-35 times for this young team to press the accelerator.

Newcomer Jeff Suppan will do it, having started 30-plus times each of the last eight seasons. Lefty Chris Capuano makes it a legitimate Big Three. And, with straightened out Derrick Turnbow teaming with Francisco Cordero, the back of the bullpen will be throwing smoke, and the Brewers won't simply be blowing smoke.

Tom Singer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.