Pears missed only two games after fracturing his leg against Carlton in round 18 before being brought back to face the Bulldogs.
""We probably made a little mistake by playing him,"" Hird said on Friday at Windy Hill.
""He had that small crack in his leg and got through half the game, and then got a significant whack on it.
""The doctors say if he rests it this week then it will be fully healed by next week so it was probably a bit of a mistake on my behalf to play him.""
Promising 21-year-old Michael Hurley will also miss the important game against the Eagles with his troublesome 'stress reaction' injury in his foot.
Hird said if Hurley had the injury at the start of the season it would be handled differently.
""It's an injury that if he had at the start of the year you'd give him a full six weeks rest, but at the moment we think we can manage it with a couple of games, rest and [limiting] his training time,"" Hird said.
""It's a hot spot in his foot and there's a chance somewhere along the line that it might crack all the way through.
""We think if we played him this week it's an unnecessary risk for him.""