i think for the following sentence,
<Based on this year's national open result, they are the 4 best player that we have for this year>
its better to add a few more words after 4 best players to make the sentence more complete,
<Based on this year's national open result, they are the 4 best players [out of all those participants] we have for this year>.
best 4 in national open doesnt mean best 4 in Singapore as not all players have participated..