More than 72,000 managers have made a direct swap from Rashford to Rondon ahead of the Tuesday 26 February deadline of 18:45 GMT.
The Argentinian played 120 minutes in Man City's Carabao Cup final win over Chelsea on Sunday afternoon.
However, with his team-mate Gabriel Jesus (£9.9m) ruled out, the 30-year-old could be set to start again on Wednesday evening.
Aguero scored a hat-trick in each of his last two home matches and will be among the top captain picks for Gameweek 28.
Part 1: GW28 Ones to watch: Kane fit and fresh
Part 2: GW28 Differentials: Sigurdsson to thrive
Part 3: GW28 Captains: Salah set for more Watford joy
Part 4: GW28 Scout Selection: Aubameyang leads the line