By Junko Fujita

KURASHIKI, Japan, March 13 (Reuters) - Texas Rangers starter Yu Darvish and Masahiro Tanaka, the New York Yankees' latest big-money signing, have much in common.

They enjoyed hugely successful high school and professional careers in Japan, both winning the Eiji Sawamura Award for the top starting pitcher and earning multiple All Star call-ups before signing mega-deals in Major League Baseball.

They also have Yoshinori Sato in common.

The 59-year-old pitching coach worked closely with Darvish at the Hokkaido Nippon-Ham Fighters and with Tanaka at the Tohoku Rakuten Golden Eagles in Nippon Professional Baseball.

While Sato expects much of the 25-year-old Tanaka, who signed a seven-year, $155 million contract with the Yankees in January, he told Reuters that Darvish is the better pitcher and part of baseball's elite.

"Darvish was a pitcher from the time he started baseball as a child and he already stood out from his early teens," said Sato in an interview in Kurashiki, western Japan, where the Eagles were playing a pre-season game.

"But Tanaka was a catcher originally and was not converted to a pitcher until high school.

"Tanaka has a lot of respect for Darvish and put in a lot of effort to become as good as him. He has reached a level where he is almost close to Darvish," added Sato, who coached Darvish at the Fighters for three seasons from his rookie year.

Tanaka and Darvish rose to fame off the back of their performances in Japan's prestigious national high school baseball tournaments in the spring and summer.

After graduating high school, Darvish joined the Fighters in 2004 as the first pick of the draft, Tanaka in 2006 joining the Eagles as top pick.

While Darvish seemed destined to pitch on the game's biggest stage, Tanaka, who went 24-0 last season for Japan's champions, may not be enjoying such success without Sato's keen powers of observation and coaching savvy.

Sato joined the Eagles as a pitching coach before Tanaka's third season in NPB. At the time, Tanaka was struggling to boost the speed of a fastball located in the lower end of the strike zone.

Sato knew what needed fixing even before he joined the Eagles coaching staff.

'BIGGEST TIP'

Late in 2008, Sato, who was taking a year off after leaving the Fighters, was watching a baseball game on television at his home in Kobe city, western Japan.

He rarely watches games on television but that day Tanaka was starting against the Fukuoka Softbank Hawks and he decided to tune in.

During the game, Sato noticed something in Tanaka's delivery - every time he stepped with his left leg, his left knee moved toward the outside. That has to be fixed, Sato thought.

He had no idea he would be coaching Tanaka the following season.

After going 11-7 in his rookie year, becoming the first player out of high school to win the Pacific League's top rookie award since Daisuke Matsuzaka, Tanaka ended his second season a less impressive 9-7.

When Sato was offered a job as a pitching coach with the Eagles, then manager Katsuya Nomura asked him to work with Tanaka to try to get the best out of him.

Sato believed Tanaka's knee movement was hindering the transfer of power to the ball and taking some of the spin off the pitch. By stabilizing the left knee, Sato thought Tanaka should be able to swing his arm more efficiently and increase the speed of his pitch.

At a training camp, Sato watched Tanaka play catch. He then told him what he thought the problem was and made sure Tanaka understood fully before implementing any changes.

The correction process began with Sato coaching Tanaka to use the modification when he was pitching lightly during warm-up and cool-down periods.

The following season, in 2009, Tanaka had 15 wins. And double-digit victories every season after that.

"Fixing the knee is one of the biggest changes to make him what he is now," said Sato. "That was the biggest tip I gave him."

While Tanaka made great strides since the knee fix, Sato said he could improve further if he could lower his hip when he throws, like Darvish does.

Sato, who pitched for 21 seasons in Japan, is also a strong believer in physical fitness and says the reason he was able to play into his 40s -- when he pitched a no-hitter -- was because he put miles into his legs.

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