Shields also had an impressive performance on April 22, allowing two earned runs and striking out five in a win over the Toronto Blue Jays. In his past two starts, the right-hander has combined for 12 strikeouts and three walks in 16 innings.
For his efforts, Shields was named the American League Player of the Week, another first for the 26-year-old.
"I wanted it bad," Shields said of Sunday's win. "These first two games were probably the most exciting games in Major League baseball this year, as far as I'm concerned. The way that we won those ballgames was huge for us. It showed our character, showed the way that we play, and the way that we're going to be playing. So coming into [Sunday's] game, we knew it would be a big game for us."
Shields outdueled Boston's ace, Josh Beckett, throwing 98 pitches over nine innings, and lowering his ERA to 1.13 over those two starts in the week. Boston entered the series leading the Major Leagues in batting average (.302), doubles (55) and on-base percentage (.374).
"He threw four pitches, [and] he threw them all for strikes," Boston manager Terry Francona said. "He changed speeds, he didn't get into any patterns. He threw the ball very well."
Beckett, who fanned a career-high 13 batters, had equal praise for his mound counterpart.
"It's not the first time he pitched pretty good, and it won't be the last time he outpitches anyone either," he said. "I think he deserves a lot of credit for what he did. He did a great job."
Shields faced just 29 batters -- two over the minimum -- issuing seven strikeouts and one walk. The lone free pass was to slugger Manny Ramirez, who stole second base and was the only Sox batter to reach scoring position.
After giving up a single to Dustin Pedroia in the first inning, Shields kept Boston's bats quiet. The third-year hurler didn't allow another hit until 15 batters later.
"I can't say enough," Rays manager Joe Maddon said. "That was outstanding."
While Shields may have been dominant on Sunday, his April 22 outing also impressed Maddon, since the right-hander clearly did not have his best stuff that day.
"Thats the competitive aspect of him. I like the idea that he's not at the top of his game yet and he's still pitching relatively well," Maddon said. "It's going to keep getting better."
Other pitchers nominated for the weekly honors were Cleveland southpaw Cliff Lee and Yankees right-hander Chien-Ming Wang.
Tigers outfielder Magglio Ordoñez and Texas teammates Michael Young and Josh Hamilton were also nominated for the award.
To recognize his achievements, Tourneau, the world's largest watch store, will supply Shields with an engraved luxury Swiss Tourneau timepiece.