Jim Jefferies and his assistant Billy Brown - familiar foes for the former Scotland boss - were last week replaced by Sergio at Hearts.
The Portuguese has been in charge for 10 days now and his Hearts players will have the added incentive of trying to impress to win a place in the team for next week's Europa League fixture with Tottenham.
Dons boss Brown said: "It does make it a little more difficult, because we don't know his strategy the way we did with Jim and Billy.
"We knew how Hearts used to play and that helped us a little. We even knew the players they preferred. Now that Paulo Sergio's seen them in training he may make some changes.
"We can't predict the opposition. That's not our concern. Our concern is can we predict our own performance, never mind the opposing team."
The Dons have failed to score in three SPL matches this season, but Brown was adamant goals will come.
He added: "We did some reasonably good things against Celtic, but we lost the match and we're not scoring goals.
"To win matches we need to be more offensive - even if we're playing away from home.
"We're making chances and we know we've got proven goalscorers in the squad. The four strikers we have in the squad are all capable given chances - but we have to create as well.
"We're not concerned unduly about it, but obviously it would be helpful if we could score a goal."
Brown hopes the Dons can take advantage of a distracted Hearts side with one eye on Spurs.
He added: "There's a lot of excitement around Tynecastle and the players will be playing against us for their places against Tottenham.
"Sometimes it's easier away from home because the pressure's on the home side, particularly Hearts, with important games coming up.
"We've got to try and get some points on the board - that's pretty obvious."
Former Celtic target Maceo Rigters has been training with Aberdeen this week and will travel to Tynecastle as an observer before returning to train at Pittodrie early next week.
Only then will Brown make a decision on a deal.
Brown added: "He's an accomplished player, but his fitness level is a bit short of what is required to go out and play."
Source: Team Talk
Source: Team Talk