JETHAWKS NOTEBOOK: CUTTER CLASSROOM CASTELLANOS PROVES TO BE A QUICK STUDY.

Byline: Gideon Rubin Staff Writer

SAN JOSE - Jonathan Castellanos was throwing on the side in advance of a spot start against Inland Empire in early June when JetHawks pitching coach Mel Stottlemyre Jr. asked him, ``Hey, you want to work on a cutter?''

``We fooled around with it a little bit, and he started feeling it that day,'' Stottlemyre said.

It's quickly become Castellanos' favorite pitch, helping him go from being the JetHawks' mop-up man the first two months to their most-effective starter in the last month.

Going into his start June 7 against the 66ers, Castellanos was 0-0 with a 7.03 ERA. Since then, he's 2-0 with a 3.41 ERA in 29 innings over six outings including four starts, and he's lowered his ERA to 5.06.

And with promotions of the JetHawks' two best starters, Matt Henrie and Lance Cormier, his emergence couldn't have come at a better time.

In his brief stint as a starter, Castellanos has become the team's stopper. Both of his victories have come after a JetHawks loss, and Lancaster is 3-0 when he pitches after a loss.

In his most recent start - on Friday, after a 14-1 loss to San Jose - he struck out eight batters and allowed two runs on eight hits and one walk in six innings and was credited with the win in a 6-3 victory over the Giants.

``I'm amazed,'' Stottlemyre said. ``I've never seen a kid pick (the cutter) up so fast and use it in a game and have that much success with it.''

The right-handed Castellanos' cut fastball tails away from right-handed hitters and bears in on lefties, and its explosive late-breaking action has made it a devastating pitch.

``It's darting, it's late, and when it's on, he's locating it so well you could almost let the hitters know it's coming and they still don't have a chance,'' Stottlemyre said.

Stottlemyre said the cut fastball has made all of his pitches, especially his slider, even better.

``Hitters will let you know how well you're pitching,'' he said. ``They had a lot of bad swings (Friday), and this is a team that's handled our pitching staff really well.''

--On hold: Plans to develop right-handed hitting outfielder Marland Williams as a switch-hitter have been put on hold for this season. Williams, who was activated last week but hasn't played in more than three weeks due to a wrist injury, will work on switch-hitting in the offseason, but his recent setback means he won't have any left-handed at-bats this season.

``Hopefully, he can get healthy and come back next year feeling really good about what he's done this year,'' JetHawks manager Mike Aldrete said.

Williams already has a lot to feel good about. After batting .246 (69 for 280) at short-season Yakima (Wash.) last season, he's hitting .294 (69 for 235) at Lancaster.

The JetHawks' parent Arizona Diamondbacks want to give the speedy Williams, who is regarded as one of the top base-stealing prospects in minor-league baseball, an extra step to first base out of the batter's box they believe would make him a top prospect.

Hitting coach Damon Mashore said if Williams can learn to hit from the left side as well as he does as a right-hander, he'll ``be in the big leagues soon.''

Williams, who returned to Lancaster after spending nearly two weeks at the Diamondbacks' extended spring training facility in Tucson, Ariz., did not play in the San Jose series but took limited batting practice, hitting two rounds of 10 pitches.

He hopes to be able to play this week.

``I'm excited to be back with the fellows,'' Williams said. ``Hopefully I can help the team out any way I can.''

--Wildfire: While he was in Tucson, Williams said smoke from a raging wildfire, which recently threatened homes in nearby Oracle, permeated the air and dominated the landscape.

``It was burning pretty bad, all you could see was smoke,'' Williams said. ``Where I was staying, you could see the fire burning over the mountains.''

--Odds and ends:!off Aldrete will spend the week vacationing with his family in Big Sur and won't report back to Lancaster until Friday, when the JetHawks open a three-game home series against Inland Empire. The Diamondbacks give all full-season managers a three-day leave, and the timing worked out nicely for Aldrete with a scheduled off day Monday, and his team playing in San Jose. Mashore will be interim manager. ...

Right-handed pitcher Mike Schultz will arrive in Lancaster on Wednesday and make his JetHawks debut in a scheduled start against Inland Empire at Lancaster on Sunday. ...

Newly acquired first baseman Edgar Varela left Sunday's game in the third inning after throwing out his back and is doubtful for tonight's game against Rancho Cucamonga.

Gideon Rubin [phone]

gideon.rubin(at)dailynews.com

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JONATHAN CASTELLANOS

JetHawks' pitcher has been a big contributor since learning to throw a cut fastball from pitching coach Mel Stottlemyre Jr. in early June.