United – who face fierce rivals Manchester City on Sunday – stuttered in the early months under the Dutchman with just three wins in their opening 10 matches.
However, with only two Premier League defeats since November they have charged up the table and find themselves locked in a battle for second with Arsenal and City.
"The key is the players, who are developing themselves in the process of what we have done with each other," Van Gaal told MUTV.
"I believe because it is not only the last five matches. I think in more than 20 games we've only lost two times, so it's a long row of matches that we win or at least don't lose.
"You have very good performances and you also have bad performances, but at the end the result is good and the key is always the players.
"The players have to do it at the right moment, at the right time against resistance. We have one more point than City now, and we're one point behind the second position in the table [Arsenal], so that speaks for itself, I think."
United have lost the last four derby matches, with Sergio Aguero's strike condemning them to a 1-0 defeat at the Etihad Stadium in November following Chris Smalling's first-half dismissal.
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