Well it depends on how excellent the saves were (random aside: as a non-goalkeeper I find it quite challenging to judge just how difficult a certain save actually was and my feeling is that most other non-goalkeepers, whether they admit or not, struggle with the same) and how bad the mistakes were, but just to throw out some numbers, say an excellent save is one that on average goalkeepers make only 5% of the time and a mistake is making a mistake in a situation where 95% of goalkeepers would not. In this situation an excellent save would be worth +0.95 goals while a mistake would be worth -0.95 goals. While I chose the numbers specifically so they would be even, intuitively I feel the value of a mistake would in most cases be roughly equal to the negative of the value of an excellent save, assuming we are limiting the discussion to mistakes during saves i.e. mistakes which lead directly to goals. For other types of mistakes, like flapping at a cross or making a poor pass which leads to an opposition attack, the value of the mistake is never as severe as the -1 goals that people usually give it, but that's another matter.
So in your example, unless the mistakes came at extremely high leverage times during the match (a contrived example: say you are 1-0 up in the 89th minute when your goalkeeper makes two mistakes in two minutes to make it 1-2, and then makes 5 excellent saves in the 91-95th minutes), a goalkeeper who makes five truly excellent saves and two mistakes is still up several goals in my book.
In general I think goalkeepers hardly ever get enough credit for making even routine saves.