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Norichika Aoki & Ryan Cook: Waiver Wire

Today’s waiver wire brings you two rookies who have come into more important roles of late, one an outfielder and one a relief pitcher.

Norichika Aoki | OF | Brewers | Owned: 3% Yahoo! and 1.7% ESPN

Aoki turned 30 years old earlier this year, but technically he’s a rookie after coming over from Japan. He opened the season as a reserve player with Ryan Braun, Corey Hart, and Carlos Gomez/Nyjer Morgan entrenched in the outfield, but he’s seen more playing time lately because Mat Gamel‘s season-ending knee injury has forced Hart to play some first base. It wasn’t just Gamel’s injury though, Aoki earned his spot.

Having started 16 of the club’s last 17 games in either right or left (plus one in center), Aoki has put together a .294/.360/.515 batting line with mostly gap power — five doubles, two triples, two dingers — and nice stolen base skills — a perfect 5-for-5 in attempts. He’s produced a .330/.390/.538 batting line over the last 30 days, though I would expect an AVG and OBP to remain closer to his recent marks as a starter going forward. Because he’s batted primarily first or second in the order, he’s more of a run scorer than a guy who will give you a ton of RBI.

Tons of players have instant success when thrust into a starting role, but two things really stand out to me about Aoki: his plate discipline and his contact skills. His walk rate is a solid 8.1% overall, but he’s swung at just 16.5% of the pitches he’s seen outside of the strike zone, the fifth lowest mark in baseball (min. 100 PA). His whiff rate is excellent at 4.8% — resulting in better than league average 12-2 K% — so Aoki is laying off pitches out of the zone and putting the strikes he does swing at in play. That’s a recipe for a higher than usual BABIP — he’s at .330 on the season — and a productive hitter.

Again, Aoki doesn’t figure to hit a ton of homers (despite the favorable home park) or drive in many runs given his lineup spot and stuff, but he should hit for a strong average, get on base, steal some bags, and score a boatload of runs hitting ahead of Braun. Now that there’s a clear opening for him to play every day, Aoki is worthy of a spot on your fantasy roster.

Ryan Cook | RP | Athletics | Owned: 24% Yahoo! and 8.6% ESPN

Oakland has received some very nice early returns from the Trevor Cahill trade as Jarrod Parker has shown the ability to be a competent big league starter (last time out notwithstanding) and Cook has emerged as a bullpen force. The 24-year-old right-hander has pitched to a sparkling 0.69 ERA this season with a 2.86 FIP to back it up, allowing him to assume a late-inning role in manager Bob Melvin‘s bullpen. Cook’s walk rate (5.19 BB/9 and 15.2 BB%) is high, though it has been inflated just a bit by intentional walks (12.5 uIBB%). The strikeout rates are strong (8.65 K/9 and 25.3 K%) and he’s yet to allow a homer.

Brian Fuentes blew a save in spectacular fashion over the weekend, forcing Melvin to re-evaluate his closer situation. He told reporters that he’s going to a closer-by-committee approach with Fuentes, Cook, and Grant Balfour as his primary end-game options. The only thing standing in Cook’s way of full-time ninth inning work is that his skipper said he’s often the best option in high-leverage eighth inning situations (via Jane Lee). Hooray for leveraging relievers, boo for fantasy owners trying to dig up saves.

Obviously Cook is not going to sustain a .119 (!) BABIP all season, but he is a fly ball pitcher in a huge ballpark, and those guys tend to have lower than usual BABIPs. The important thing is that he’s pitched his way into the late inning mix while both Fuentes and Balfour are impending free agents and trade bait. With the A’s starting to fall out of the race and the trade deadline drawing closer, Cook could go from holds machine to the latest saves guy in the East Bay.