Foyth was chasing a loose ball in midfield as Simpson gained posession near the halfway line.
As Simpson collected the ball, Foyth lunged in high with his right boot, digging the studs close to the Bournemouth man’s knee.
Referee Craig Pawson walked over to Foyth before brandishing his second red card of the afternoon.
The Argentine looked shell-shocked with his hands on his heads but walked off as Bournemouth players tended to their injured team-mate.
Tottenham were reuced to 10 men in the first half after Heung-min Son acted out of chracter and barged Jefferson Lerma to the floor.
The South Korean reacted angrily to an inital tussle with Ryan Fraser and when Lerma tried to pick up the ball once Son had won a free-kick, the forward couldn’t help himself.
Lerma’s initial challenge seemed innocuous but Son pushed the Cherries midfielder to the floor and was shown a straight red by Pawson.
The game is a must-win for Spurs who need to secure Champions League qualification and give them the boost they need ahead of next week’s Champions League clash with Ajax.
If Tottenham fail to beat Bournemouth and Chelsea win their game in hand against Watford, the Blues would go level on points with their London rivals.
A loss for Spurs and a Chelsea win would put Maurizio Sarri’s men in third place.
Manchester United and Arsenal are fifth and sixth and need their top four rivals to drop points.
Mauricio Pochettino and co. should finish the season in the top four but a slip up against the Cherries and in their last game against Everton would welcome some unwated nerves.
Son and Foyth will now miss their next three Premier League games, a ban that will carry into next season.
Son will return to the side to face Ajax in the Champions League, though.
The winger was badly missed by Spurs in the first leg at their new stadium as they lost 1-0 to high-flying Ajax.
Harry Kane also remains out for the season with an ankle injury but Spurs are hopeful he can return for the Champions League final, should they make it.