PITTSBURGH (AP) — Like most of his brethren, Chicago Cubs manager Rick Renteria is getting a handle on Major League Baseball's expanded replay system.
And just like everything else with the perpetually rebuilding club, the learning curve is steep.
The Cubs were on the wrong side of two replay reviews in Monday's 1-0 opening loss to the Pittsburgh Pirates, including an overturned call in the top of the 10th that allowed Neil Walker to hit a game-ending homer off Carlos Villanueva in the bottom of the inning.
Chicago's Emilio Bonifacio singled with one out in the top of the 10th and was ruled safe when he dived back to first on an attempted pickoff by reliever Bryan Morris.
Pirates manager Clint Hurdle trotted out to challenge the call, which was overturned by replay officials in New York.
"I'm still trying to figure out what the 'clear and convincing evidence' is supposed to be," Renteria said. "It's a work in progress. They have a lot of people looking at those videos in New York, so they must get it right."
The largest regular season crowd in the 14-season history of PNC Park (39,833) roared when Bonifacio was ruled out and the din only grew louder when Walker smacked a Villanueva (0-1) changeup into the right field seats.
"This one feels pretty special," Walker said. "This is a special day for this team, this organization. We've come a long way."
Walker's first career game-ending homer easily cleared the Clemente Wall while his teammates rushed onto the field in celebration. It was the first opening-day walkoff homer for the Pirates since Bob Bailey's off San Francisco's Juan Marichal in a 1-0 victory in 1965.
Bonifacio went 4 for 5 for Chicago, but the Cubs were 0 for 11 with runners in scoring position and wasted a fine start by Samardzija, who scattered five hits over seven innings.
"I was happy with the way I kept the ball down in the strike zone," Samardzija said. "It helped to get the double plays because they made the overall outing look a little better than it really was."