Rusney Castillo will have an instant mentor with the Red Sox. Everything he is about to do, Yoenis Cespedes did three years earlier.

Cespedes actually had his best season as a rookie in 2012 after defecting from Cuba and signing a four-year, $36 million deal with the Oakland A's. Now with the Red Sox, the outfielder already has imparted advice to Castillo, an outfielder who will soon be his teammate after finalizing a seven-year, $72.5 million contract over the weekend.

"I told him (Saturday), 'This is the same game. It's the same baseball,'" Cespedes said Sunday through translator Adrian Lorenzo after going 3-for-4 with an RBI in the Red Sox's eighth consecutive loss, 8-6 to the Seattle Mariners. "It may be a little better quality of baseball, but it's the same game. I told him, 'You don't have to try to be somebody you're not. Just be yourself and play the way you play, and you're going to do well.'"

Cespedes seems to have taken his own advice in making the move from the A's to the Red Sox.

Acquired in the July 31 blockbuster that sent ace lefty Jon Lester to Oakland, he is batting .259 with four homers with the Red Sox. Since the trade, he leads the team with 18 RBIs and has driven in 23 percent of the team's runs.

"He's had timely extra-base hits," manager John Farrell said. "He's put us ahead on a number of occasions. He's got strength, he's got bat speed, he's got plate coverage. He's put up quality at-bats a majority of the time for us."

The Red Sox are hopeful Castillo will play for them next month. And when he arrives, it will be helpful to have Cespedes -- "a tangible comrade," said Brodie Van Wagenen, Castillo's agent -- by his side.

"He's obviously a player I've admired for a long time," Castillo said through Lorenzo's translation. "I'm happy to be a member of the Red Sox with him."