Hille, 29, had his training load reduced last week after experiencing soreness in his knee, while Gumbleton hurt his in the middle of last month and was ordered to rest.
Both had operations on Tuesday and are expected to be back in full training before Christmas.
The news comes as another blow for the 22-year-old Gumbleton, whose short career has been plagued with injuries although he managed 17 senior games this year.
Meanwhile, 20-year-old defender Pears, who suffered a bruised pancreas in June that ended his season, will have surgery on the foot that already had him in the Bombers' rehab group.
"We have had a few minor setbacks and I want to emphasise that they are minor, but we have three operations over the next two days," general manager of football operations Paul Hamilton told essendonfc.com.au on Wednesday.
"We have had some concerns with Tayte's foot for a little while and he is having surgery on that today.
"The doctors are telling us that the problem we have got is only a minor problem but it will keep him off the track for four weeks.
"Our club doctor, Bruce Reid, is very confident that he will be well prepared for the season that is ahead."
On Tuesday, coach James Hird said defender Cale Hooker would return to full training next week after being placed on modified duties last week following a hamstring strain.
"He tore his hamstring quite badly in the last round of the year so we're just taking that pretty slowly," he said.
"He's been training for a few weeks but we've taken him out of this week. There's no problem at all with Cale."
Hird also denied Andrew Welsh had suffered a setback despite the midfielder ending Monday's training session early and icing the groin he had surgery on in August.
"He's doing about half the training load at the moment. We're just making sure we don't flare that up again," he said.
