Will power quotient rise for Ellsbury?

BRADENTON, Fla. -- A day after Jacoby Ellsbury hit his first home run of the spring -- and first home run anywhere since he took Brian Bass of the Orioles deep on Sept. 20, 2009 in Baltimore -- Red Sox manager Terry Francona was asked how many home runs he thought Ellsbury was capable of hitting this season.

“I don’t know,’’ he said. “That’s sort of one thing we don’t ever talk about because you get yourself in a bind. He takes a swing like he did yesterday, it’s gorgeous. It’s certainly there. But I think you start putting numbers on guys, that’s the last thing we want to do is try and do that. That’s when you get in trouble.’’

Ellsbury hit nine home runs in 2008, his first full season in the majors, averaging a home run per 61.6 at-bats. He hit eight in 2009, or one for every 78 at-bats.

But check the career arc of some other top base-stealers, and there is reason to suspect that Ellsbury is at a stage of his career where double figures in home runs are well within reach. Hall of Famer Rickey Henderson had his first double-digit season in home runs in his third season, when he hit 10 home runs. By his fifth season, he was up to 16, and two seasons later he hit 28, a career high he would match later. Henderson wound up hitting 297 career home runs.

Hall of Famer Lou Brock reached double figures in his third full season, when he hit 14. He reached double figures in home runs seven times in his 19-year career.

Johnny Damon went from eight home runs to 18 in his third full season, then reached double figures in 11 of 13 seasons, topping out at 24 with the Yankees in 2006, a number he matched with the Bombers in 2009.

Marquis Grissom was in his second full season when he hit 10 or more home runs, and had 13 straight seasons of double figures in home runs, topping out at 23.

And Ellsbury’s new teammate, Carl Crawford, was in his second full season when he hit 11, and has followed that with double-figure home runs in five of the next six seasons, including a career-high 19 in 2010.

When Ellsbury was asked Saturday if he recalled his last home run, he made light of it. “Every day in batting practice,’’ he said. “I don’t think about stuff like that.’’

There is a stat favored by some analysts called ISO, which stands for isolated power and measures a hitter’s raw power. A simple way of calculating it is to subtract a hitter’s batting average from his slugging percentage. There are other formulas that give equal weight to doubles and triples. But a slugger like Albert Pujols has an ISO percentage of .293. Ellsbury’s, by contrast, is just .114, as 75 percent of his hits have been singles (98 extra-base hits, 301 singles).

So it’s highly unlikely that Ellsbury will take on a slugger’s profile. But double figures in home runs are well within his reach and probably to be expected going forward.

“You just don’t know,’’ Francona said. “Over the course of a guy’s career, you just don’t know what it’s going to turn into. Youk [Kevin Youkilis], I never thought that would be Youk. If [Ellsbury] gets on base at a higher percentage, that’s way more important than hitting home runs. If he can be a guy who gets on base at .380, .400, that’s more important.’’

Ellsbury enters this season with a career .344 on-base percentage.

Still, Francona agreed with the notion that more home runs are not an unexpected outcome.

“As guys get at-bats, they know their body, they learn the league, they learn their swing. He certainly has the ability. That ball [Saturday] went a long way.’’

Interestingly, in an earlier conversation this spring, veteran outfielder Mike Cameron said he believes Ellsbury should bunt more.

“Two or three times a series,’’ he said. “It would open up so many things for him.’’