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08/09/11 6:57 PM ET

Mechanical adjustment made Frieri tighten up

NEW YORK -- Credit reliever Ernesto Frieri for being receptive to making a mechanical change to help remedy his command issues.

If only his back was just as enthusiastic.

Frieri was placed on the 15-day disabled list on Monday with a lower back strain -- the result, he said, of a mechanical adjustment he tried to make recently, in addition to the late flight the team took Sunday from Pittsburgh to New York.

"After the flight from Pittsburgh, my back felt really, really bad," Frieri said. "I couldn't sleep."

Frieri has been working with pitching coach Darren Balsley on trying to help harness his command, which has been amiss at times this season, as he's walked 29 and also hit nine batters in 46 appearances and 49 1/3 innings.

"I want to say the main reason this happened is changing my mechanics ... trying to step straight [toward the plate] and get on top of the ball instead of throwing across by body like I do," Frieri said. "But that wasn't comfortable."

Frieri said his back was feeling better Tuesday. When he's cleared to throw again, he will work again with Balsley on his command.

"I've been fighting all year to find the strike zone," Frieri said.

Guzman's production for Padres tough to ignore

NEW YORK -- Jesus Guzman hasn't been in the Major Leagues with the Padres for two months, yet he has already made a lasting impression on San Diego general manager Jed Hoyer.

And apparently plenty of others, Hoyer said Tuesday.

"Judging off the number of comments on him by other teams, he's made himself noticed. He's put himself on the map," Hoyer said.

Entering Tuesday's game against the Mets, Guzman, who has primarily played first base since his promotion from Triple-A Tucson on June 16, was hitting .339 and has five home runs and 28 RBIs in 122 plate appearances.

He was slotted third in the order in the second game of a four-game series with the Mets.

Guzman, who took a nine-game hitting streak into Tuesday's tilt, was hitting at a .378 clip and led all Major League players with 24 RBIs since the All-Star break.

Better still, Guzman hit .380 with 24 RBIs in 21 games since July 16.

"He's always hit in the Minor Leagues and now he's shown that, given the extra chance in the big leagues, he can hit here," Hoyer said.

Guzman, 27, was hitting .332 with Tucson before he was promoted. He has played some third base and left field, but has mostly played first base.

That Guzman has been on such a tear at the plate hasn't necessarily surprised the Padres, who signed him to a Minor League contract in November.

Guzman is a career .305 hitter in the Minor Leagues, with a .373 on-base percentage. His only taste of the Major Leagues before this season came in 2009, when he had 20 at-bats with the Giants.

Has Guzman essentially cemented a spot for himself on the 2012 roster? Manager Bud Black said to ask him again the end of the season, when Guzman's sample size is more substantial.

"He's a good hitter, and right now, he's swinging the bat very well, there's no doubt about it," Black said. "Let's keep it going. At the end of the year, let's look at it again.

"Every day is a test and right now, he's passing every test with flying colors."

Darnell the latest Padres rookie to debut

NEW YORK -- When rookie James Darnell took the field for his Major League debut on Tuesday, he became already the 10th player to make his Major League debut this season with the Padres.

The previous rookies to do so were pitchers Anthony Bass, Erik Hamren, Even Scribner and Josh Spence. The position players include catcher Luis Martinez, infielders Logan Forsythe and Anthony Rizzo and outfielders Cedric Hunter and Blake Tekotte.

According to Elias, the last time that the Padres had at least 10 players make their Major League debut was in 2009, when the team had 15 debuts.

The Padres finished 75-87 that season.

Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.