The team said that he had a bilateral hernia repaired.
"Recovery time is approximately 6 weeks & it is anticipated that he will be on or close to a regular schedule for the 2019 season," the Pirates tweeted.
On Wednesday, Archer tweeted a picture from his hospital room and thanked fans for the amount of support he has received.
Thanks for all the love and support guys. It truly means a lot. I'll be back and I'll be better. pic.twitter.com/H5YezI0NyD— Chris Archer (@ChrisArcher22) November 28, 2018
Archer, 30, went 6-8 with a 4.30 ERA and 162 strikeouts in 148 1/3 innings last season.