Need an impact arm or bat that can give your fantasy team a boost? Whether you're looking for an injury replacement or someone to stash on your bench, the fantasy waiver wire has a plug or long-term fix to pick up today. Check out the following 10 players -- all sitting on waivers in many leagues, and all ready to help your team in Yahoo Sports Fantasy Baseball, the Official Commissioner Game of MLB. All statistics and ownership percentages are as of Wednesday.
Trevor Williams, starter, Pirates (44% owned)
Coming off a solid rookie season in which he compiled a 4.07 ERA and a 1.31 WHIP in 150 1/3 innings, Williams has been even better as a sophomore with a 3.44 ERA and a 1.20 WHIP over 136 frames. The 26-year-old has been lights-out over his last seven starts, posting a 0.86 ERA and a 1.10 WHIP while limiting opponents to a .212/.272/.288 batting line. If he keeps it up, Williams could be primed to finish the season with a flourish.
Shane Bieber, starter, Indians (40% owned)
Bieber has quietly been one of the best rookie hurlers in baseball this year, going 8-2 with a 4.52 ERA and a 1.34 WHIP in 14 starts since debuting on May 31. He's pitched better than his numbers suggest, as they're still inflated by July 24 loss against the Pirates in which he allowed seven earned runs in 1 2/3 innings. In his other 13 starts, he has a 3.80 ERA and a 1.28 WHIP. Bieber's also been hurt by a .358 BABIP, which helps explain the difference between his ERA and his 3.34 FIP. Based on his stellar peripherals -- including a 9.4 K/9 rate and a 1.7 BB/9 rate -- the 23-year-old is poised for a strong September.
Lucas Giolito, starter, White Sox (24% owned)
Giolito's first full season has had its ups and downs, as the former first round Draft pick currently leads the Majors in earned runs (94) and the American League in walks (75) while posting a 5.85 ERA. He's turned it around lately, however, going 5-2 with a 4.09 ERA and a 1.16 WHIP over his last nine starts. The 24-year-old has made great strides with his command during that time, notching a 2.3 K/BB ratio after tallying an even number of walks and strikeouts over his first 17 starts of the season. He's pitching deeper into games as a result, averaging over six innings per start over his last nine outings compared to fewer than 5 1/3 innings previously. So despite his disappointing overall numbers, Giolito is trending in the right direction.

Ryan Madson, reliever, Nationals (23% owned)
Madson was activated from the 10-day disabled list Monday -- the same day that closer Kelvin Herrera landed on the DL with a potentially season-ending left foot injury. With Sean Doolittle still working his way back from the disabled list, the door is open for Madson to pick up some saves in the near future. Although the 38-year-old has struggled this year with a 5.28 ERA and a 1.42 WHIP, Madson is a proven closer with 91 career saves under his belt. For fantasy owners in need of saves, Madson is capable of providing a short-term boost.
Melky Cabrera, outfielder, Indians (21% owned)
Cabrera is making the Indians glad they re-signed him in July after releasing him in June. In his second stint with Cleveland this year, he's batted .314/.385/.533 with six home runs and 16 RBIs in 34 games, proving he's still an effective hitter at age 34. After posting four seasons with an OPS of .800 or greater from 2011-2016, Cabrera is flirting with that number again this year at .781.
Jakob Junis, starter, Royals (21% owned)
After an impressive rookie season in which he went 9-3 with a 4.30 ERA and a 1.28 WHIP in 98 1/3 innings, Junis has continued to make strides as a sophomore, raising his strikeout rate from 7.3 K/9 to 8.5 K/9 while ramping up his workload. He also notched his first career complete game on Tuesday, capping off a terrific August in which he flashed a 2.95 ERA with a 1.15 WHIP and a 4.8 K/BB ratio in 36 2/3 innings. If last month's performance is any indication, the 25-year-old could be headed for a big September.

Luke Voit, first baseman, Yankees (20% owned)
Since being traded from the Cardinals on July 29, Voit has seen his playing time increase due to Greg Bird's offensive struggles. In 12 games with the Yankees, Voit's batting a scalding .351/.400/.595 with three homers and nine RBIs, providing some lift for an offense that's been without Aaron Judge, Didi Gregorius and Gary Sanchez. The 27-year-old has recently been penciled into the heart of the order as a result, which boosts his fantasy value in the near term until the aforementioned trio returns.
Luis Urias, second baseman, Padres (14% owned)
Urias, MLB Pipeline's No. 22 overall prospect, made his MLB debut Tuesday against the Mariners. The 21-year-old is regarded as San Diego's second baseman of the future after batting .306/.397/.405 during a promising Minor League career, which included a .296/.398/.447 showing in 120 games for Triple-A El Paso this season. While his power is still developing, the table-setter's ability to hit for average and get on base make him worth adding in deeper leagues.

Billy McKinney, outfielder, Blue Jays (10% owned)
Acquired from the Yankees as part of the July 26 trade for J.A. Happ, McKinney has been on fire since making his Blue Jays debut on Aug. 18. In 10 games since being called up, the 24-year-old has smacked three home runs while slashing .367/.486/.767 with nine RBIs. He's batted leadoff in four of those games, as his strong batting eye (6:8 BB/K ratio) makes him well-suited for hitting at the top of the order. If McKinney remains there, he could prove to be a sparkplug for Toronto's offense, especially with Josh Donaldson expected back soon from a calf injury.
Tyler O'Neill, outfielder, Cardinals (9% owned)
With the Cardinals' outfield depleted by injuries to William Fowler and Marcell Ozuna as well as the trade of Tommy Pham, O'Neill has seen his role increase over the past month. The 23-year-old rookie has helped his case by catching fire at the plate, batting .333/.367/.644 with four home runs and 10 RBIs in 17 games dating back to July 31. He's primarily batted third or fourth during that stretch, emerging as a potent middle-of-the-order bat for St. Louis. With four homers in his last five games, O'Neill is peaking just in time for fantasy playoffs.