Tomkinson was banned for three weeks yesterday after he pleaded guilty to a dangerous tackle in the win over the Brumbies in Canberra on Saturday night.
Tomkinson went in high on Brumbies fullback Tom Banks and was given a yellow card by referee Nic Berry.
Tomkinson can count himself lucky as his shoulder collided with the head of Banks.
The citing commissioner found the tackle met the red-card threshold and sent the incident to a hearing.
Tomkinson has been suspended for three weeks and will miss the clash against the Crusaders in Christchurch on Friday, the Rebels at Forsyth Barr Stadium and the Bulls in Pretoria.
Foul Play Review committee chairman Adam Casselden said the tackle of Tomkinson was an act of foul play and merited a mid-range punishment of six weeks. Any incident of foul play involving the head must have a punishment starting at six weeks.
Taking into mitigating factors such as his clean record and guilty plea, the suspension was reduced to three weeks.
Tomkinson (23) will be disappointed to miss three games but he could have been sent from the field on Saturday night with a red card which would have caused his team plenty of problems.
Last season, in the opening game of the year against the Chiefs in Hamilton, Tomkinson was shown a red card for a tackle late in the game.
But the Highlanders successfully challenged the decision and Tomkinson was not punished and did not have to sit out any games.
This year he probably should have been given a red card in Canberra but received only a yellow.
The Highlanders will most probably look to bring back Tima Fainga'anuku on to the wing or give a starting debut to Chris Kuridrani.
Meanwhile, it all appears to have worked out well for former Highlanders assistant coach Glenn Delaney.
The former assistant coach moved after two seasons with the Highlanders to be the defence coach at the Llanelli Scarlets in Wales.
Brad Mooar was the new head coach at Scarlets but his stint at the club has been cut short by his decision to return to New Zealand and join the All Black coaching staff.
Mooar will return to New Zealand at the end of the Welsh club season.
Delaney has now become the head coach for Scarlets in the 2020-21 season.
He had previously coached overseas before coming home to coach Canterbury for a year and then the spell in the South.
The Scarlets are third in conference B in the Pro 14 league.