"You can't play everybody. I've talked to Heisey about it already," Baker said on Saturday. "That's a very valuable person on your team, which I've tried to explain to everybody before. That's like my sixth man in basketball. They should give an award like they do for the sixth man in basketball. That person is invaluable."
In 2012, Heisey often split time in left field with veteran Ryan Ludwick. But it was Ludwick who emerged as the regular by midseason. Ludwick was re-signed to a two-year, $15 million contract as a free agent in December.
Heisey, 28, avoided arbitration last month by signing a one-year, $1.325 million contract. Last season, in 120 games with 80 starts, he batted .265 with seven home runs and 31 RBIs while establishing career highs in at-bats (347), hits (92), doubles (16) and triples (5).
"He can pinch-hit, play all three outfield positions if somebody goes down for a period of time," Baker said. "He hasn't shown quite yet if he can play every day or not. People want you to throw him out there for a month or two months, it doesn't work like that. Most chances come in days. They don't come in months."
Heisey is batting .329 with six homers and 22 RBIs in 76 lifetime at-bats as a pinch-hitter.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon This story was not subject to the approval of Major League Baseball or its clubs.