They were the standout players for Port on the day which saw the team suffer at 25-point loss at Simonds Stadium.
Monfries kicked a career-best seven goals, while Lobbe had 59 hitouts, the third highest of all time.
Joel Selwood received maximum votes, with both Ken Hinkley and Chris Scott judging him as best on ground.
Travis Boak currently leads Chad Wingard by a solitary vote on the Port Adelaide leader board; comfortably leading the third-placed Hamish Hartlett.
Justin Westhoff and Kane Cornes round out the top five.
Geelong v Port Adelaide
10 Joel Selwood (Gee)
6: Angus Monfries (Port)
5: Shannon Motlop (Gee)
4: Matthew Lobbe (Port)
2: Cameron Guthrie (Gee)
2: Steve Johnson (Gee)
1: Corey Enright (Gee)
Port Adelaide AFLCA votes leader board
55: Travis Boak
54: Chad Wingard
38: Hamish Hartlett
36: Justin Westhoff
27: Kane Cornes
