Photos on the Web site "The Cheater's Guide to Baseball Blog" appeared to show how Rodriguez, in two games against the Texas Rangers, habitually adjusted the brim of his hat before pitches -- and that there was a white substance visible under the brim.
Rodriguez denied the allegations, saying the substance was built-up resin from his use of a rosin bag on the mound. Major League Baseball agreed.
Angels GM Bill Stoneman said baseball disciplinarian Bob Watson called the team and said "there's nothing to it, nothing to investigate."
Cleared by MLB, Rodriguez had some criticism for Derek Zumsteg, the blogger whose handiwork focused the baseball world's attention on the underside of Rodriguez's hat.
"It's easy for a guy sitting at his desk, watching television, to put pictures on the Internet," Rodriguez said, according to the Los Angeles Times. "But I hope he has something better to do than to mess with people. He has no clue what he's writing about. I don't even know who he is."
Zumsteg, reached by e-mail, told the Times "I understand where from his side it seems like he's been singled out and persecuted for what's a fairly common practice, and if baseball's going to crack down on him they should certainly look around the league at other pitchers with pine tar on their hats. I brought this up as something I found interesting in connection with my work on the book, and it's not at all personal."
After last year's World Series, MLB is paying more attention to rule 8.02b, its dictum on pitchers using foreign substances on the baseball.
In Game 2 of last year's World Series, cameras showed a brown substance on Kenny Rogers' left (throwing) hand in the first inning, and St. Louis manager Tony La Russa brought it to the umpires' attention. Rogers' hand was clean when he came out for the second inning.
Rogers insisted then that mud, resin, spit and dirt was what everyone saw at the base of his left thumb -- not pine tar or anything else illegal.
In February, baseball's playing rules committee approved changes that would eject and suspend players for intentionally defacing or discoloring a ball. Umpires have the discretion to issue only a warning if they determine a pitcher didn't intend to alter the characteristics of a pitch. Previously, such a pitch was called a ball, a warning was issued and the violation was announced.
Players can be suspended up to 10 games for violating the rule.
Information from The Associated Press was used in this report.