Pirates call up Gregory Polanco

— -- PITTSBURGH -- Gregory Polanco has made his major league debut.

The Pittsburgh Pirates called up their coveted outfield prospect late Monday night after placing second baseman Neil Walker on the 15-day disabled list. Polanco started in right field against the Chicago Cubs on Tuesday night. He hit second and went 1-for-5 with a run during the game, a 7-3 Pirates loss. 

Pirates fans have been waiting eagerly for Polanco to arrive, and the outfielder said he is "grateful" for the positive response on social media to his call-up.

"I didn't know it was going to be like that," Polanco told reporters prior to Tuesday's game. "I appreciate that and am very grateful."

"When you have a player like this come to the major leagues, it's like graduation day," Pirates manager Clint Hurdle said. "It's a day for the organization to celebrate, especially those on the scouting end and in the player development department. We're excited to have him here."

Polanco was hitting .347 with seven home runs in 62 games for Triple-A Indianapolis this season. The 22-year-old from the Dominican Republic said he called his mother to inform her of his promotion, which he claimed was a surprise to him.

"I had no idea," Polanco said. "They just said keep playing hard and your time will come. I've been waiting all my life. I made it. It made me feel proud of myself."

ESPN Baseball Insider Keith Law ranked Polanco as the 13th-best prospect in baseball entering the 2014 season and moved him up to No. 3 in his latest rankings released late last month.

Polanco's 47 runs scored led the International League, and his batting average and OPS (.945) each ranked second.

"I feel proud playing where Clemente played," Polanco said. "I'm going to give it all I got."

Walker experienced abdominal pain shortly before Pittsburgh's 6-2 win over the Cubs on Monday and underwent an emergency appendectomy.

He tweeted Tuesday that he's feeling better while admitting he was upset to miss Polanco's debut.

ESPNChicago.com's Jesse Rogers and The Associated Press contributed to this report.