The tackle was reviewed by referee Hollie Davidson and the television match officials during the game, with a change in direction from Niniashvili before the collision deemed a mitigating factor to downgrade the incident from red to yellow.
At a disciplinary hearing on Tuesday, Underhill accepted he had committed an act of foul play but did not accept it warranted a red card.
The committee determined it was a mid-range offence, which would warrant a six-week ban, and downgraded it to four due to Underhill’s remorse. But they were unable to reduce it further due to his prior record.
The 28-year-old was given a three-week ban in April after also being sent off by Davidson during Bath’s Challenge Cup round of 16 victory against Pau in April.
Underhill, who has 41 caps for England, has made 13 appearances for Bath this season.
