Jonas was cited for reckless rough conduct against St Kilda's Dylan Roberton in the second quarter of Port Adelaide's five-point win over the Saints on Saturday night.
His conduct was graded as high contact and high impact.
The charge originally carried a four-match ban, but an early guilty plea would lower the suspension to three weeks.
Port Adelaide's general manager of football, Peter Rohde, told portadelaidefc.com.au the club was not willing to risk Jonas being suspended until Round 22.
"Given the classifications for the offence, we felt the chances of him getting off, or getting his suspension lowered, were slim," Rohde said.
"We didn't feel it was worth taking on at the tribunal and risking the extra week (suspension)."
The young defender received messages of support from the club's supporter base and the wider football community on Twitter last night, drawing the following response from Jonas:
I like to think I'm a tough but fair player...but rules are rules. Thanks for your support. #illbeback
— Tom Jonas (@twjonas42) July 22, 2013
Jonas will be available to return from suspension when Port Adelaide hosts the Gold Coast Suns at AAMI Stadium in Round 21.