The final winning margin of 11 points makes the game look a more comfortable win than what it was, as Thunder trailed by 23 points midway through the second quarter.
However, Chavis, who scored 34 points, then came to the fore as he got his first basket with a slam dunk and Thunder never looked back.
They continually closed the deficit, before they went ahead for the first time since the early exchanges with four minutes to play. Thunder then extended their lead in the final few minutes to record a sixth win from as many home matches this season.
Chavis said: “I can’t even explain how happy I am. I’m tired but we won and that’s all that matters. We all focused in, listened to what coach said and started to get steals and easy baskets.
“I didn’t even know how many points I had. I’m out here to win and make sure my team-mates get better as well as myself, that’s all I’m focused on.
“It’s always good to start the league season with a win, no matter how it was at first.”
Thunder coach Daniel Hildreth, in his programme notes, had said it was important that his side did not get themselves behind, before a last-minute comeback – after that situation occured when the sides met in the National Trophy two weeks ago, as Thunder won 92-89, having trailed by 14 points at one stage.
Worthing were slow to get going in the opening ten minutes, though, which was summed up when Hildreth changed four of his starting players at the same time with 1min 39sec remaining of the stanza.
Westminster, with former BBL players Michael Martin and Julius Joseph in their line-up, led 29-14 at the end of the first quarter and they continued to dominate in the early stages of the second period.
Thunder missed too many openings and Westminster increased their lead to 39-16 midway through the second quarter. From there, Chavis led Thunder’s fight-back as a 8-0 run narrowed the visitors’ lead.
Westminster led 46-34 at half-time but Thunder continued to close the gap throughout the third stanza.
Joseph got into foul trouble when he picked up his fourth of the game with 3-24 left of the period and Thunder finished the quarter with a 7-0 run to tie the game at 55-55 heading into the final ten minutes.
Worthing could have taken the lead into the final period but Hank Rivers missed a pair of free throws with a second left.
Thunder did not take the lead until two three-pointers in quick succession from Jakub Bogusz gave them a 72-70 advantage. From there, they did not look back as they continued to increase their lead to run out comfortable winners in the end.
Rivers also had a dominant performance for Thunder with 20 points and 14 rebounds, while Tomas Seduikis sank 12 points. Martin top-scored with 22 points for Westminster.
Hildreth said: “They were 23 points ahead and the guys that play the majority of the minutes for us were just not pulling their weight.
“I spoke to those guys individually and as a group that they needed to step up and lead us through and we made a change in defence, which definitely helped.
“I’m just very pleased that we were able to show character to come back and come away with a 11-point win.”
Thunder travel to Leicester in the league on Saturday, before they host Worcester Wolves 2nd in the National Cup on Sunday (5pm).