Seedorf – who spent a decade as a player at the Serie A giants – was appointed in January to replace the sacked Massimiliano Allegri.
Despite a recent run of four successive wins, Milan still sit 10th in the table and the San Siro board have failed to back Seedorf amid suggestions he will be sacked at the end of the season.
They host arch rivals Inter in a crucial derby on Sunday and ahead of the clash, De Jong, who acknowledged Seedorf is still getting used to the role, believes the damage was done earlier in the season.
"The derby is a special game and we faced it before with Massimiliano Allegri's philosophy," De Jong told Il Giornale.
"We have understood our mistakes now. The move from Allegri to Seedorf, with that change of philosophy, complicated the situation.
"For me Milan are a team who belong in the top two places. If the results are inadequate, then at the end of the season everyone has to look in the mirror and ask why.
"Being a coach is a different profession to being a player.
"He (Seedorf) has just started with four months under his belt, so he is learning.
"Perhaps Seedorf talks a bit too much, so he needs to gain experiences. He is a winner, loves Milan and knows how it feels to wear this jersey."
