All the players retained and bought for the 2017/18 season of the ISL.
The Uruguayan striker was NorthEast United's top scorer in the ISL last season.
The question regarding the number of foreigners in I-League teams remained unanswered following the AIFF League committee meeting.
CK Vineeth is set to rejoin Kerala Blasters for the upcoming ISL season, having confirmed his departure from Bengaluru on Tuesday.
The 63-year-old Gregory will succeed Italian Marco Materazzi, who guided Chennaiyin to the title in the 2015 season.
Both Chhetri and Udanta have signed three-year extensions that will keep them at Bengaluru till the end of the 2019-20 season.