Vietnam play two 2022 World Cup qualifiers against Malaysia and Indonesia soon.
Before the King's Cup tournament in May Park had gone to Europe to take a look at and meet the two Vietnamese-origin players, but things have not turned out as expected.
The South Korean, speaking at a press meet in Hanoi on Monday, said: "A few things concerned me after the trip. Firstly, many such players do not speak Vietnamese. They have lived in Europe most of their life, so they act and think like a native. I am deeply concerned about this difference. I wonder if they can fit in with other Vietnamese players when they return."
Not many overseas Vietnamese players have been successful in Vietnam. Even famous names like goalkeeper Dang Van Lam and striker Mac Hong Quan, who are fluent in the language and have good understanding of the culture, struggled in the beginning.
Park said: "If a player is really talented, we need him. But if he is just as good as a domestic player, we have to consider.
"It is slightly different when it comes to goalkeepers because it is a unique position. A goalkeeper does not communicate much."
That might open the door for Vietnamese-Czech keeper Filip Nguyen, who recently applied for Vietnamese citizenship.
Nguyen, 27, and 1.90 meters tall, is the main goalkeeper of Slovan Liberec, one of the most successful clubs in the Czech Republic.
Dang, 29, scored 13 goals for Norwegian first division club Nest-Sotra Fotball last season, becoming the league’s top striker. Both have publicly expressed their desire to don the Vietnamese jersey and contribute to Vietnamese football.
The Vietnamese Football Federation (VFF) said it is willing to facilitate any Vietnamese-origin player wanting to return and contribute to Vietnamese football.