A final berth against either Liverpool or Barcelona will be at stake when the Dutch giants arrive at the Tottenham Hotspur Stadium on April 30, with the return leg in Amsterdam scheduled to take place eight days later.
Spurs will be without talismanic forward Son in the home leg as he serves a one-match ban for picking up three yellow cards over the course of the earlier rounds.
The 26-year-old has contributed 19 goals in 43 appearances for the Lilywhites across all competitions this season, emerging as one of the best players in the Premier League.
Despite being forced to sit out the huge clash with Ajax , Son is confident Mauricio Pochettino's men can still get the job done without him.
"I try to be positive but missing this semi-final makes me so sad, so disappointed," he told Sky Sports .
"I'm a very positive guy, I'm very comfortable with the lads so I'll probably be more nervous watching in the stands than when I play.
"But I trust my team, I trust my players, I trust this stadium so I'm not worried about it.
"Saturday is more important for me, so I'll give everything for my team to get three points and then Champions League is next.
"I want to play every single game. I'm the guy who enjoys my football, with joy and of course I want to play the semi-final."
Son will likely retain his place in Tottenham's starting line up this Saturday as they host West Ham in a crucial Premier League fixture .
After featuring in 50 matches for club and country this season, Son could be forgiven for relishing the prospect of an upcoming break, but he insists he is still feeling fresh and ready to contribute.
"I'm fine. I'm happy, the same as every else," he added. "The players have done very well, playing well, training hard and enjoying it.
"I'm the most positive guy. I try to be positive and bring positive energy."