The Hammers admitted irregularities in registering the players, but after Mascherano's move to Liverpool in January, Tevez remained as the center of controversy in England.
The FA imposed a record $11M on West Ham, but four Premiership clubs sounded their objection with the decision, as they demanded further points deduction.
Blatter stressed that FIFA will deal with the situation, with or without other clubs' persuasion.
"We are monitoring this situation very carefully and we will ourselves look at the files once it has been dealt with by the English league and the Football Association," Blatter told a media briefing at FIFA headquarters in Zurich on Tuesday.
"We will look at this, and not only if we are asked. We will do it anyway."
Tevez led the Hammers to a terrific finish to the Premiership campaign, winning seven games from nine, to secure a Premiership place at the expense of Sheffield United and Charlton.
On the other hand, Sheffield United Chairman Kevin McCabe told BBC Sport that he believes West Ham should be relegated instead of his side, following the Tevez saga.
"I feel cheated because losing to Wigan was not the root cause of our relegation," he said.
Ironically, Wigan Chairman Dave Whelan backed McCabe's case, claiming that Tevez's registration was illegal.
"We need a new hearing because he has been registered illegally again. That should be another fine or points deduction," Whelan told reporters.
"I cannot believe the Premier League will allow these things to happen and put Sheffield United into the Championship and leave West Ham in, it is not right, not fair."
However, the FA played down possibilities that the Hammers would be subject to further sanctions.