RECAP | BOX SCORE
SAN JUAN, Puerto Rico -- Puerto Rico's first game in the World Baseball Classic was a tougher test than many expected.
"We swung at too many first pitches. We'll be talking about that to the team because we need to address that," Puerto Rican manager Jose Oquendo said.
Javier Vazquez got help from his bullpen, and Williams' single up the middle scored Alex Cintron in the fifth inning to put Puerto Rico ahead before a home crowd of more than 19,000 at Hiram Bithorn Stadium.
With a roster that also features major league stars Carlos Beltran, Carlos Delgado and Ivan Rodriguez, Puerto Rico is a heavy favorite to finish among the top two teams in its group and advance to the second round. Cuba and the Netherlands are also in Pool C.
Team Panama manager Anibal Reluz Vasquez still thinks his team can make it to the next round.
"We will stay motivated to win this championship and we'll keep fighting," he said. "Today we had more chances to win than Puerto Rico, but it just didn't work out."
Bruce Chen, Panama's best pitcher, will go to the mound Wednesday against Cuba.
"Tomorrow we will bring Bruce Chen, who may be our best card in the stack," Reluz Vasquez said. "We have done some strong scouting on Cuba. We've played them a lot in the past and they're going to have to bring their best tomorrow to beat us."
Rios was down 0-2 in the count in the fifth before his home run tied the score at 1.
"I was very proud," he said. "I saw the left fielder getting close to the wall, but I felt very proud when the ball went into the stands."
That chased Panama starter Lenin Picota after 60 pitches.
"He threw strikes and my boys were anxious," Oquendo said.
Cintron followed with an infield hit. A sacrifice bunt by Alex Cora sent Cintron to second, and Williams gave Team Puerto Rico the lead with a signature line drive that split the diamond and bounced into center field.
Vazquez left in the fourth with two on and none out. He threw 57 pitches.
"Vazquez was working too fast and he was pitching a little too high in the strike zone," Oquendo said.
Federico Baez loaded the bases with a walk to Ruben Rivera, and Carlos Ruiz walked to force in the first run of the game. But Baez escaped by getting a fly ball and a double-play grounder.
Panama also threatened in the first, putting runners on first and second with none out. Olmedo Saenz hit into a fielder's choice, forcing Orlando Miller at third for the first out.
Panama returned the favor in the bottom half. Puerto Rico manager Jose Oquendo gave the hit-and-run sign to Rodriguez with one out, but Beltran struck out and the runner was thrown out at second.
Lee missed a two-out RBI opportunity for Panama in the fifth when he grounded out, leaving a runner on third.
The winning pitcher was Jose Santiago, who went 1 2/3 innings. Manuel Acosta took the loss.
Puerto Rico plays the Netherlands on Wednesday, and Panama plays Cuba.