We have officially put the first month of the baseball season in the books, and plenty of waiver wire sleepers have already developed for all league formats including NL-Only and AL-Only leagues. That seemed to go rather quickly, but like they say, time flies when you're having fun. This is usually about the time when less experienced fantasy owners begin to panic when one of their top picks is still not producing. The baseball season is incredibly long, and while a poor month for a top fantasy pick disappointing, it's still roughly only one-sixth pf the season.

Don't Overreact 

Take Mark Reynolds' 2013 season for example. Reynolds had a scorching April last year, belting eight home runs with 22 RBI and a .301 batting average. With his average up, and strikeout rate down for the month, there were rumblings that Reynolds had finally found his stroke in Cleveland - Terry Francona had figured something out with the super streaky third baseman, and that Reynolds may have found a home with the Tribe.

Then May came, and Reynolds' numbers dipped to five home runs, 19 RBI, a .219 batting average, and 34 whiffs in 30 games. The next month he struck out 40 times in 26 games. By August, Reynolds was filling a bench role for the Yankees after being granted his outright release from Cleveland. After an April and May that produced a .255 batting average with 13 home runs and 41 RBI, Reynolds would bat only .195 with eight home runs and 26 RBI.

In other words, it is not smart to get too high or too low on players after only one month of the baseball season. That said, it's still wise to keep an eye on your waiver wire , just in case a cold start turns into a season long slump. This is especially important in league specific formats where the number of available players is cut in half.

Waiver Wire Sleepers for NL Only Leagues

Luckily, Rotoballer  is here to guide you towards some possible hidden gems that may still be on your waiver wire. Check here every week for some NL-Only guys to watch, players who may still be available in your league.

Nate McLouth, Washington Nationals, OF

5% owned CBS, 3% owned Yahoo!

Owning Nate McLouth can be maddening, as he is not only one of the streakiest players to have during a season, but it's difficult to even know what you'll get from him year to year.

McLouth looked on the fast track to stardom during his days in Pittsburgh, before disappearing almost completely after being traded to Atlanta in 2009. After becoming a fantasy afterthought, McLouth bounced back as a top-50 fantasy outfielder in 2013 as a member of the Baltimore Orioles.

At his best, McLouth is an exciting combination of 20-homer, 30-steal potential. At his worst, McLouth is an injury risk who's free swinging and strikeout rate will kill your batting average. Last year we saw the good, as McLouth's  12 homers, 30 stolen bases, and 76 runs scored easily made him one of the more valuable waiver additions in fantasy.

This year, McLouth is in a fourth outfielder role in Washington, and the bad Nate McLouth is what we've seen so far. With Bryce Harper on the shelf for the next two months or so, however, McLouth becomes an interesting add, especially in NL-only leagues, as a guy who could get in a groove with regular playing time. Any player who offers a quality power/speed combo has the chance to become instant gold in fantasy leagues.

If you need an outfielder in NL-only leagues, McLouth becomes a guy you need to keep an eye on. I would even venture to call him a must add for anyone who lost Bryce Harper.

Brandon Hicks, San Francisco Giants, 2B/SS

6% owned CBS, 2% owned Yahoo!

Need some pop, or having some issues at your middle infield? Well, meet the Brian Dozier of NL-Only leagues.

Getting a chance at playing time due to Marco Scutaro's injury, Hicks has shown some major pop in Scutaro's abscence, as he's belted five home runs, while driving in nine, and scoring 11 times. That's pretty solid production, but when taken in to account that Hicks has done this in only 64 at-bats, it becomes really eye opening.

There are two downfalls with Hicks that will keep me from calling him an NL-Only must add. First, Hicks is surely going to return to a bench role when Scutaro returns. And second, Hicks is currently batting less than .220, a bi-product of his astronomical strikeout rate. Not only has Hicks struck out a whopping 25 times in the aforementioned 64 at-bats, but he's had at least one K in all but five games. That's getting into Mark Reynolds territory.

If you can survive the obvious batting average hit, Hicks is worth a look due to the fact that home run production can be sparse at the second base and shortstop position. In fact, only three NL middle infielders (Troy Tulowitzki, Jhonny Peralta, and Neil Walker) have hit more home runs than Hicks so far this year. Even if it's a short run, a hot Hicks could really help your power output.

Brandon McCarthy, Arizona Diamondbacks, SP

16% owned CBS, 5% owned Yahoo!

If owners in your league have left Brandon McCarthy on waivers, don't follow suit, and definitely don't be scared off by a first month that saw the Arizona righty go 0-5 with a 5.54 ERA. When you look past the numbers, there is a lot to like here with McCarthy, and I'm willing to call him a must add in all NL-Only leagues.

McCarthy has been throwing the ball much harder this season, and it's caused an uptick in strikeouts. With 34 Ks in 37 innings, McCarthy is averaging close to a strikeout per inning. That's elite territory, and somewhere that McCarthy has never been.

So what's wrong here? Well, McCarthy has been a victim of the long ball. He's already given up a league leading seven of them through his first six starts. Is it a problem? Sure, but it's a problem that has been seen with plenty of pitchers who discover increased velocity. Almost half of the seven home runs McCarthy has allowed came in his second start of the season, when he was tagged three times by the Rockies in Colorado. I'm willing to bet that, even if McCarthy allowes more dingers than he has in the past, that he settles down to a HR/9 that fantasy owners can live with.

If you're looking for evidence that McCarthy has figured it out before you add him, you may have already seen it in his last loss. Despite allowing only two earned runs, and striking out 12 batters through seven innings, the Diamond backs were shutout.

Now is the time to add McCarthy if he is still available in your league for the chance that he's on the upswing. The Diamondback's starting rotation has been decimated, meaning that even if McCarthy has a few more rough starts, he's has little chance to lose his rotation spot. In NL-Only leagues, where pitching can get thin quickly, adding McCarthy speculatively makes a lot of sense.