After an off-day Monday, Mark Prior will face right-hander Carl Pavano in Game 6 at Wrigley Field on Tuesday night with the Cubs leading 3-2 in the best-of-seven series.
Prior has won 12 of his last 13 decisions with a 1.55 earned-run average, including a 2-0 record in the postseason.
And if the Cubs don't win Game 6, they'll have another chance Wednesday night in Game 7 with Kerry Wood on tap.
"No, we've only got one chance," Cubs left fielder Moises Alou said. "We're going to do it Tuesday. We can't worry about Wednesday."
Not that the series needs any more intensity, but Game 6 figures to be a high-strung affair with Prior on the mound and an angry Sosa looking to even the score.
Beckett knocked him backward in the third inning with a high-and-tight fastball on his first delivery that caused Sosa to stagger and point angrily at the pitcher while debating with plate umpire Larry Poncino.
"He overreacted a lot," Beckett said. "I don't know really what else to say. I don't know what we was trying to dotrying to pull a Red Sox-Yankees thing. I don't know. I was so surprised I had to shout something else back at him. It was kind of baffling to me, really."
Sosa has been hit in the head twice this season, including April 20 in Pittsburgh when Pirates reliever Salomon Torres broke his helmet and sent him to the hospital for tests.
Montreal's Zach Day also beaned him on Sept. 9 in San Juan, Puerto Rico, though Sosa was able to remain in the game.
After Sunday's game, Sosa said Beckett "probably wasn't" throwing at him, but added his angry reaction was based on being hit in the head before.
"I have nothing against nobody," he said. "I like to play the game the way it is. But when I don't like something, I'm going to let him know."
Marlins catcher Ivan Rodriguez intervened with Sosa and told him the pitch was unintentional.
Sosa said he replied: "I understand, but I've been hit in the head a couple times. I don't like that anymore. That [stuff] has to stop."
The Cubs hit an NLCS-record 10 home runs in the first four games, but it was the Marlins who played long ball Sunday.
Beckett held the Cubs without a hit through 42/3 innings before Alex Gonzalez's bloop single in the fifth. The only other hit was Alou's single with one out in the seventh.
Cubs manager Dusty Baker and several players said it was difficult to see the ball in the twilight because of the late-afternoon start.
"That was tough," Sosa said. "Even though [Beckett] pitched a great game, the shadows were tough too."
What was the main difference between the Beckett who was shelled early in Game 1 and the Beckett who looked unhittable in Game 5?
"The first game was at 7:05 (p.m.) and this one was at 4 o'clock," Sosa said. "You can see the ball better at 7:05. I'm not making excuses because the guy pitched a great game. But, you know "
After keeping his emotions in check in his last start in an effort to change his mound demeanor, Zambrano was back to his first-pumping, sky-pointing ways in Game 5.
Baker said he told him beforehand to "be yourself" and Zambrano got in and out of jams. Zambrano escaped bases-loaded situations in the third and fourth innings, retiring Derrek Lee on a force play to end the third and striking out Luis Castillo to end the fourth.
After Miguel Cabrera walked with one out in the fifth, Lowell connected on a hanging slider with two outs to give the Marlins a 2-0 lead.
"There were many hard hit balls off him," Cubs pitching coach Larry Rothschild said of Zambrano. "But he hurt himself with the walks."
Rothschild said it was important for Zambrano to get back in his comfort zone, no matter how emotional he gets on the mound.
"That's his style," Rothschild said. "We tell him not to show anybody up, but he's an emotional guy."
Emotions will be running high Tuesday, when the Cubs will have an opportunity to win their first pennant since 1945 in front of their own fans.
"If we had to pick two guys on the staff to throw right now, you'd pick Prior and Wood," Cubs first baseman Eric Karros said. "But that doesn't guarantee anything."