Which surprise teams will have staying power?

It's early in the Major League Baseball season, but only two teams favored in the preseason to win their divisions - the Detroit Tigers and San Francisco Giants - are sitting in first place.

Let's take a look at some of the more surprising early season contenders and forecast how long they might be able to stay in their respective races:

COLORADO ROCKIES (18-13, second in National League West): What an utter mess this team's pitching situation was last year. After watching the starting pitchers struggle for a couple months in 2012, then-manager Jim Tracy opted for a unique approach: Use a four-man rotation, but put the starters on a 75- pitch count.

The results were disastrous. Colorado finished 64-98 and in last place in the NL West. Their team ERA was a miserable 5.26. To put it in perspective, the second-worst NL team ERA last year was Houston's 4.62.

This season, Colorado has a 3.87 team ERA, which ranks eighth in the NL. Given the Coors Field effects, the Rockies are never going to have one of the best ERAs in the league, so their performance has been commendable.

An offense led by Carlos Gonzalez, Troy Tulowitzki, Dexter Fowler and young catcher Wilin Rosario is going to carry its own weight through a 162-game season. The big question is whether the Rockies' pitching can hold up well enough to enable the team to be in division title contention.

Two keys have been the return to health of Jorge de la Rosa, who is 2-3 with a 4.18 ERA in 32 1/3 innings, and a respectable performance out of nowhere from newcomer Jon Garland, who had been neither healthy nor effective since the 2010 season with San Diego.

The bullpen, led by closer Rafael Betancourt and hard-throwing lefty setup man Rex Brothers, has been superb, except for Wilton Lopez (4.91 ERA).

Can the success continue? On the positive side, Jhoulys Chacin, who posted a 1.46 ERA in four starts before getting injured, is back in the rotation. Also, Roy Oswalt was signed as a free agent last week, so he could possibly be joining the rotation sometime in June.

On the down side, the Rockies don't have anyone remotely resembling an ace, and most of their pitchers have a checkered injury past. It doesn't seem likely that Colorado will manage a win total of more than the low 80s.

PITTSBURGH PIRATES (17-14, second in NL Central): The Pirates have posted 20 consecutive non-winning seasons. The last time they ended up .500 or better was in 1992, when they lost the NL championship series.

Could this be the year Pittsburgh becomes a winner again? The Pirates have gotten off to a positive start, even though they merely rank in the middle of the pack in both pitching and hitting.

Probably the big key to their success has been the bullpen. In his first full season as a major-league closer, journeyman Jason Grilli has been the best at his job in the NL. He's 12-for-12 in save opportunities with a 0.69 ERA.

Primary setup man Mark Melancon has been just as effective, with a 0.56 ERA in 16 innings. Basically, when the Pirates have managed to take a lead into the late innings, they have consistently nailed down the win.

Offensively, things figure to get a little better than they've been, too.

Andrew McCutchen, a 2012 MVP candidate, is off to a mediocre start and should pick up his production the rest of the way. Neil Walker got off to a sluggish start before going onto the disabled list.

Ideally, Pittsburgh could use another big bat, and it's getting tougher and tougher to accept No. 8 hitter Clint Barmes��� complete lack of offense (.192 average, four RBI). The pitching staff lacks a true ace, but there's a chance elite prospect Gerrit Cole could arrive on the scene to provide that sometime this summer.

Pittsburgh should have its best shot at a winning season in a long time, particularly if it can add some reinforcements at the trade deadline. If the Pirates can add a hitter who can give McCutchen some protection in the lineup, they might be capable of making things a little more interesting than favored Cincinnati would expect in the NL Central.

KANSAS CITY ROYALS (17-11, second in American League Central): The Royals have kind of been the Pirates of the AL. Although they've had a winning record as recently as 2003, their playoff drought has actually been longer; Kansas City���s last postseason game was its Game 7 victory over St. Louis in the 1985 World Series.

With a group of young, homegrown offensive players in the lineup, the Royals were a popular pick to be a breakout team in 2012. It didn't happen. Last year's Royals stumbled to a 72-90 record, which was merely a one-game improvement over 2011.

There have been two big keys to the turnaround this year. First, Kansas City got off to a quick start, which was not the case when it opened up 3-14 in its first 17 games last year. Second, the Royals finally have top-flight pitching to complement their young offense.

Former Tampa Bay pitcher James Shields has come aboard to become the Royals' ace. Another newcomer, Ervin Santana, has been outstanding. The Royals' team ERA is second in the AL at 3.33.

That strong pitching has helped make up for a slow start from Kansas City���s offense. The Royals rank only 12th in the AL with 122 runs scored. Based on potential, the team should improve offensively, although Mike Moustakas (.198 average, one homer, six RBI) and Eric Hosmer (.258, 0, 9) have really underperformed. Unexpectedly, the Royals rank last in the majors with 16 home runs.

Kansas City isn't going to seriously threaten Detroit for NL Central supremacy, but a winning record is a strong possibility if (when?) the offense picks up.

BOSTON RED SOX (21-11, first in AL East): OK, a team with a payroll Boston's size and with its recent history of winning probably isn't so much a surprise contender. Still, the Red Sox went 69-93 in 2012 and finished last in the AL East, so there weren't too many people picking them to win the division this year.

There's a long way to go, and the competition in the division should still be considerable, but Boston has baseball's best record.

What's gone so right? First and foremost, Clay Buchholz (6-0, 1.60 ERA) has been the league's best starting pitcher. As a team, the Red Sox rank fifth in the AL with a 3.64 ERA. Last year, Boston was 12th in the AL with a 4.70 ERA, with Jon Lester (4.82 ERA) and Buchholz (4.56 ERA) being the chief disappointments.

Offensively, Boston ranks fourth in the AL with 158 runs scored. The Red Sox should continue to have one of the better hitting teams in the league, with guys like Dustin Pedroia, Jacoby Ellsbury and David Ortiz on board.

If Boston's pitching can continue to shine, there's no reason the team can't go from worst to first this year. The biggest roadblock will be the quality of the competition. The New York Yankees, Baltimore Orioles and Tampa Bay Rays all have rosters that appear capable of winning the AL East, too.