Jason Castro's power can provide depth at a weak position. (US Presswire)

Each week, Baseball Press will be providing some "Under the Radar" fantasy players for NL-only leagues, AL-only leagues and mixed leagues. We'll review the diamonds in the rough on the waiver wire who might help you boost your fantasy team in 2013. This edition of Under the Radar will cover potential pickups for your team that may be available early on in the season.

With all of the unpredictable injuries, job changes, and trades of the baseball season, many fantasy owners are looking to the waiver wire for help. Regardless of where help is needed, this edition of UTR can provide you with some players who are still available in most mixed leagues.

*Owned percentages via Yahoo!

Mixed League Options
Chris Johnson - 1B/3B, Atlanta Braves (29% owned)
Juan Francisco was recently designated for assignment by the Braves, opening up a clear path of playing time for Chris Johnson. Johnson was a hot pick-up earlier this season when he was on absolute fire at the plate, but has cooled down during the past two-plus weeks with the bat. Don't let the cool down deter you from adding him though, as he is still a solid .275 hitter with a little bit of pop, and now hitting every day in a very potent offensive lineup.

Jason Castro - C, Houston Astros (21% owned)
Jason Castro has often shown teases of a breakout at the plate, only to have them end due to an injury. Right now, he is showing again what he is capable of with the bat, hitting over .400 with three home runs in the last two weeks. If he can stay in the lineup, we may finally see what this 25-year-old catcher is capable of. Castro, slugging over .460 this season, is currently hitting third in the lineup for the Astros on a regular basis.

Yunel Escobar - SS, Toronto Blue Jays (8% owned)
We have all heard about how Yunel Escobar is a cancer in the clubhouse over the past few seasons,but he is currently showing why he was once a top-10 fantasy shortstop. If you are a believer in once you show a skill you own it, then you know what Escobar has done over the last 50 at-bats - a .298 average, one home run, and 12 RBI is sustainable. As long as he keeps hitting, Joe Maddon will keep slotting him in the Rays starting lineup, which is a win-win for everyone.

Marcell Ozuna - OF, Miami Marlins (9% owned)
A few weeks ago, right after his Major League debut, Marcell Ozuna was mentioned as an NL-Only option in the site's Under the Radar. At that time, he had yet to prove he could truly handle big-league pitching, but 100 at-bats later, he is hitting .318 with one home run and three stolen bases. These are not eye popping numbers, but it seems he won't be over-matched at the plate, and the counting stats will always be inhibited while hitting in the current Miami lineup. The Marlins would be hard pressed to send the youngster down when Giancarlo Stanton returns, making him a great option for the rest of the season in most mixed leagues.

NL-Only Options
Erik Kratz - C, Philadelphia Phillies (1% owned)
After a strong spring training, Erik Kratz was not able to maintain that performance once the games began to count. He was always destined to become a backup to Carlos Ruiz once he returned from his 25-game suspension, but Ruiz has hit the disabled list, and Kratz's bat is starting to heat up. His .333 batting average with four home runs in his last 30 at-bats are stats worthy to be added in a deep mixed league, but with only short term value - until Ruiz comes off the DL - Kratz is currently better suited for NL-Only action.

Chris Coghlan - OF, Miami Marlins (0% owned)
The former 2009 National League Rookie of the Year is starting to take full advantage of the playing time he is getting because of Juan Pierre's struggles at the plate. Because Chris Coghlan can play all three outfield positions well, he will continue to see consistent at-bats to make him worthy of an add in NL-Only leagues. His at-bats may decline when the already mentioned Giancarlo Stanton is healthy again, but his little bit of power and ability to steal bases, makes him good for the short term.

AL-Only Options
Leonys Martin - OF, Texas Rangers (8% owned)
Since he is not the top prospect in the Rangers organization, Leonys Martin eased his way into the major leagues with minimal fanfare compared to some other players making their Major League debut this season. He seems to have worked his way into a center field platoon with Craig Gentry the past few weeks, and will see a majority of the starts being a left-handed hitter. His bat plays better than it really is in Texas, which is a good thing for fantasy owners. Since he is being set up to succeed by being benched against lefties, there is no reason for him not to be owned in an AL-Only league.

J.D. Martinez - OF, Houston Astros (2% owned)
J.D. Martinez made a noticeable debut in 2011, carrying a .274/.319/.423 triple-slash line, with six home runs, and 35 RBI in 208 at-bats. His 2012 was disappointing, and he wasn't even projected to be a full time player for this season, but with all the changes due to performance and injury in the Astros roster, Martinez is getting consistent at-bats once again. Since being recalled on May 7, Martinez has an .807 slugging percentage, hitting three home runs, with 12 RBI in 67 at-bats. It's hard to project what Bo Porter will do down the road with his outfield, but Martinez has the job for the foreseeable future.