Wassall had registered one win and one defeat in his brief stint in charge, but his side ensured that they became a stronger threat in the automatic promotion race through Jacob Butterfield's early strike in the East Midlands.
The Rams had their backs against the wall in the closing stages but Wassall was impressed with two aspects of his team's display at the iPro Stadium.
Wassall said: "Six points in four days is a great return and what pleased us most tonight was that the first half we showed what we can do in terms of playing football, but in the second half we showed the other side to our game which is resilience and determination to come out with a result.
“Blackburn are very dangerous from set pieces as we saw and they threw everything at us in the latter stages with throw-ins, corners and crosses all entering our box.”
Last weekend, Wassall had faced the prospect of losing both of his opening matches since replacing Paul Clement in the dugout, but a stunning fightback at Brentford seems to have helped Derby turn the corner.
They had previously gone eight games without a win in the Championship, but back-to-back triumphs have moved the club into fifth place in the standings, just six points adrift of leaders Hull City.
Derby are next in action on Saturday lunchtime when they make the short journey to Molineux to face Wolverhampton Wanderers, who are currently on a seven-game winless streak.