Mbappe and Messi, the leading scorers with five goals apiece, will go up against each other at Lusail Stadium on Sunday when defending champions France meet Argentina.
Klinsmann, who won the trophy with West Germany in 1990, said it was vital to have players who could unlock defences.
“You need to have players capable of going one against one, players who can get past defenders,” Klinsmann, a member of FIFA’s technical study group, said on Saturday.
“Be risky, be courageous, because the middle of the field is so well-organised.”
The trend of teams crowding central areas has led to a sizeable uptick in the number of goals scored from crosses (45) – almost double the total (24) from the previous World Cup in Russia.
Klinsmann cited Spain, who crashed out to Morocco on penalties in the last 16, as an example of a team who paid the price for a lack of a cutting edge.
Despite monopolising possession and attempting more than 1,000 passes, Spain had just one shot on goal over 120 minutes against a stubborn Morocco.
“That style only works if you have efficiency in the box and score goals,” said Klinsmann.
Former Arsenal manager Arsene Wenger, FIFA’s football development chief, said Spain lacked a killer touch in Qatar.
“They have to develop in positions where they are not strong enough. But Spanish football will come back,” he said.
“The characteristics of modern football are everyone defends and attacks. The explosive side… running to get in behind the defensive line without the ball is very important,” he added.
Wenger said France and Argentina had adjusted well to the demands of the World Cup, praising the response of the South Americans after a shock 2-1 loss to Saudi Arabia in their opening match.
“Long balls have been used a lot to go over the defenders and pace has played an important part,” said Wenger.
“France and Argentina are two teams who learned quickly.
“It’s never easy to get to the final after losing the first game. The coach quickly found the right balance in the team in the second game.”
AFP