The waiver wire is full of gems right now, as several viable hitter and pitcher options have emerged in recent days. Those who need a lineup boost or a complete overhaul should strongly consider the 10 players listed below.
Erick Aybar, shortstop (Angels): Aybar -- who is hitting .313 this month -- was recently promoted to the leadoff spot when manager Mike Scioscia decided to shake up his struggling lineup. The 31-year-old has compiled a career .277 batting average and he possesses enough speed to swipe some bases. Hitting in front of Mike Trout, Albert Pujols and Kole Calhoun should give Aybar plenty of chances to score runs.
Jung Ho Kang, shortstop (Pirates): By hitting .316 with a pair of homers and three steals across 95 at-bats, Kang has earned a regular spot at either third base or shortstop. The 28-year-old rookie hit 40 homers last season in the Korea Baseball Organization, so there is the potential for more power as he continues to get comfortable in the Majors. Mixed-league owners should find Kang a bench spot and then gauge his effectiveness in the coming days.
Chris Colabello, outfielder (Blue Jays): Since being recalled on May 5, Colabello has hit .372 with three homers and 12 RBIs across 78 at-bats. The 31-year-old has been playing regularly in right field, and he could become the full-time designated hitter once Jose Bautista is ready to return to his regular spot. Colabello should be a mixed-league asset until he cools off, and he could be a productive long-term option if he can continue to draw daily assignments in baseball's highest-scoring lineup.
Leonys Martin, outfielder (Rangers): The Rangers' lineup has heated up in recent days, but Martin may have missed the memo as he is still hitting .210 on the season. But the speedster is a career .258 hitter, and he is on pace for roughly 25 steals this season after topping the 30-steal mark during each of the past two campaigns. Martin should also see his average improve when his current .243 BABIP rises closer to his .314 career mark, and more hits will likely mean more steals.
Marlon Byrd, outfielder (Reds): Speedsters are often plentiful on waivers, which makes the powerful Byrd a desirable free-agent commodity. One of just 21 players with 10 homers this season, the slugger should see his current .213 average rise closer to his .276 career mark when his .222 BABIP normalizes toward his lifetime .324 level.
Billy Burns, outfielder (A's): Even on a waiver wire stacked with speedsters, Burns stands out as a possible difference-maker. The outfielder -- who swiped 128 bases in the Minors across the 2013-14 seasons -- has accumulated seven swipes across 89 Major League at-bats this year. The 25-year-old is currently hitting .292, and Burns could earn regular playing time while the club covers the extended absence of Coco Crisp.
Tanner Roark, starter (Nationals): After posting a 2.85 ERA and a 1.09 WHIP across 31 starts a year ago, Roark would have been a popular draft-day commodity had he not been relegated to the bullpen due to the Nats' outstanding rotation depth. However, the right-hander has rejoined the starting five due to an injury to Doug Fister, who could miss an extended period of time with a forearm injury. As a result, Roark should be owned in virtually all leagues until Fister finds his way back to the active roster.
Charlie Morton, starter (Pirates): Because of a mediocre strikeout rate, Morton will not make a big splash in mixed leagues. But the right-hander kept his ERA below 3.75 and his WHIP below 1.30 during each of the previous two seasons, so he could be a fine streaming option. Because he plays in a pitcher-friendly National League park, Morton should have several desirable matchups during the coming weeks.
Tsuyoshi Wada, starter (Cubs): The return of Wada to the Cubs' rotation has generated little buzz in the fantasy community, despite the hurler's respectable ratios (3.25 ERA, 1.24 WHIP) across 13 starts in 2014. The 34-year-old southpaw has compiled a career 8.2 K/9 rate, and he may be a valuable source of strikeouts and quality frames in the coming weeks.
Sean Doolittle, reliever (A's): It is rare for fantasy owners to find a top-tier closer on the waiver wire, but Doolittle could be available in shallow leagues. The 28-year-old recently returned from the disabled list and should resume his ninth-inning work by the beginning of June. Tyler Clippard has done a fine job filling in for Doolittle, but Clippard excelled as a setup man in Washington and should return to that role once Doolittle logs a few effective innings. The southpaw -- who has compiled a lifetime 0.91 WHIP and 10.5 K/9 rate -- will likely be a dominant stopper for the remainder of the season.
Fred Zinkie is the lead fantasy baseball writer for MLB.com. Follow him on Twitter at @FredZinkieMLB. This story was not subject to the approval of Major League Baseball or its clubs.