It turns out they were right.
Polanco was awarded first after a replay review and Harrison followed with a drive to right for a two-run homer, leading Vance Worley and the Pittsburgh Pirates to a rain-delayed 5-3 victory over the Chicago Cubs on Saturday night.
Jordy Mercer went deep for the second straight day and Andrew McCutchen had a tiebreaking RBI single for Pittsburgh, which had lost four of five. Worley (1-0) pitched into the seventh inning for his first win with the Pirates.
Harrison's fifth homer with two out in the seventh made it 5-2 and came after Polanco was the beneficiary of baseball's replay system. He was originally called out by umpire James Hoye in a close play at first after he hustled down the line on his sharp grounder to shortstop.
"He looked safe, so you go out and you have your people run the replay," Hurdle said. "As sure as you are, you don't know until you know. It turned out to play very big for us."
The review also extended Polanco's hit streak to 11 games, making him the first NL player to begin his major league career with such a streak since Juan Pierre hit in 16 straight games for Colorado in 2000.
It was a small opening, and Harrison made the most of it when he connected against Justin Grimm.
"We know we get on base any time, we can make things happen," said Harrison, who rolled his left ankle on a swing earlier in the game. "I just happened to be in position and got a pitch and didn't miss it."
Anthony Rizzo hit a two-run homer for Chicago, which had won four of five. Eli Whiteside doubled home Darwin Barney in the seventh.
"The guys keep battling, they keep playing," Cubs manager Rick Renteria said. "That was a big pick-me-up that ball Whiteside hit up in left-center field and Barney hustling. The guys kept playing."
The start of the game was delayed for 2 hours, 1 minute while a storm passed through the area.
Rizzo's 15th homer, a drive to the bleachers in right in the fourth, gave the Cubs a 2-1 lead. The big first baseman, making a case for a spot on the NL All-Star team, is batting .318 (27 for 85) with seven homers and 19 RBIs in his last 23 games.
Pittsburgh responded in the fifth. With two outs and runners on first and second, Harrison and McCutchen each singled back up the middle to put the Pirates back in front. Brian Schlitter then replaced Travis Wood with runners on the corners and retired Russell Martin on a bouncer to third for the final out.
Wood (7-6) allowed four hits, walked three and struck out four. The left-hander had won each of his last two starts, including a season-high eight innings of three-hit ball in a 3-0 victory at Philadelphia in his previous outing.
"We got a little wild for a little bit, brought the ball up a little bit where they could find some holes and put some runs on the board," Wood said.
Worley gave up three runs and five hits in 6 2-3 innings. The righty, who was acquired in a March 25 trade with Minnesota, pitched seven shutout innings in his first start of the season last Sunday at Miami.
"Used all his pitches, pounded the strike zone, gave us a real good effort," Hurdle said.
Jared Hughes got the final out of the seventh, Tony Watson tossed a perfect eighth and Mark Melancon struck out the side for his 11th save in 14 chances. It was Melancon's first opportunity since Hurdle announced on Friday he was removing struggling righty Jason Grilli from the closer role.
The Pirates played without speedy outfielder Starling Marte, who left the team to attend to a personal matter in his native Dominican Republic. Jose Tabata got the start in left and went 0 for 3 with a walk.
Hurdle said he thinks Marte will be back in time for Monday night's game at Tampa Bay.
NOTES: McCutchen was shaken up after he took a hard tag to his head when he stole second in the fourth inning. He stayed in the game after a trainer and Hurdle came out to check on him. ... Cubs RHP Jason Hammel (6-4, 3.02 ERA) faces RHP Brandon Cumpton (2-2, 5.82 ERA) in the series finale on Sunday.