Arrieta was placed on the 10-day Injured List on Wednesday. The upcoming surgery will be to remove a bone spur in his pitching elbow. Arrieta has not pitched six-plus innings in his last seven starts, in part due to the pain caused by the spur.
"I wanted to try and make it work for as long as possible," Arrieta told reporters on Thursday. "I realized that I'm not able to give the team what it needs. The pain is something I can deal with, but it's the loss of feel and the ineffectiveness as the outings wear on. I think that the time is right to make it happen now and get a guy in the rotation that has pitched really well for us and give him an opportunity to get back to the form where he was at earlier in the season for us. I think we'll be in good hands."
The 2015 National League Cy Young winner ends 2019 with a 4.64 ERA and 110 strikeouts in 135 2/3 innings. Arrieta's 4.89 FIP in 2019 is his worst mark since his second season in 2011.
Arrieta signed a three-year, $75 deal with the Phillies in March 2018. He posted a 3.96 ERA last year in 31 starts.
The Phillies entered Saturday seven games back of the Braves for the lead in the National League East.