WASHINGTON — Roger Clemens was acquitted Monday on all charges that he obstructed and lied to Congress in denying he used performance-enhancing drugs to extend his long career as one of the greatest and most-decorated pitchers in baseball history.Fierce on the pitching mound in his playing days, Clemens was quietly emotional after the verdict was announced. “I’m very thankful,” he said, choking up as he spoke. “It’s been a hard five years,” said the pitcher, who was retried after an earlier prosecution ended in a mistrial.This case was lengthy, but the deliberations were relatively brief. Jurors returned their verdict after less than 10 hours over several days. The outcome ended a 10-week trial that capped the government’s investigation of the pitcher known as “The Rocket” for the fastball that he retained into his 40s. He won seven Cy Young Awards, emblematic of the league’s best pitcher each year in a 24-year career with the Red Sox, Yankees, Blue Jays and Astros.The verdict was the latest blow to the government’s legal pursuit of athletes accused of illicit drug use.A seven-year investigation into home run king Barry Bonds yielded a guilty verdict on only one count of obstruction of justice in a San Francisco court last year, with the jury deadlocked on whether Bonds lied to a grand jury when he denied knowingly taking performance-enhancing drugs.A two-year, multicontinent investigation of cyclist Lance Armstrong was recently closed with no charges brought, though the U.S. Anti-Doping Agency filed formal accusations last week that could strip the seven-time Tour de France winner of his victories in that storied race. Armstrong denies any doping.