Bost and Sidney, in just their second game paired together this season, combined for 49 of the Bulldogs' 69 points in a five-point win, and a disastrous 69-64 loss for Ole Miss.
Bost did most of the damage. The senior point guard had 25 points on 9 of 16 shooting. Sidney had 24 points.
"Didn't do a very good job on (Bost)," Ole Miss head coach Andy Kennedy said. "Didn't do a very good job on Renardo. (Dee) made us pay time and time again.
"It was a pathetic effort on our part, starting with me."
Bost has given Ole Miss fits throughout his career. Thursday was no different.
He had 16 points in the first half, including a 3-point make as the buzzer sounded for halftime. Bost has now scored 25 points in back-to-back years against Ole Miss in Oxford, both MSU wins.
"It's very obvious that Dee had a much better rhythm tonight," Mississippi State head coach Rick Stansbury said. "He controlled the flow of the game tonight."
Ole Miss (12-5, 0-2 SEC) has lost three consecutive games to the in-state rival Bulldogs (9-7, 1-1) in the series.
The Rebels are 0-2 in league play for the first time since 2007. Chris Warren led the team with 25 points. Zach Graham followed with 13 points, but was held scoreless in the second half.
"Tonight we needed someone to step up and make a play," Kennedy said. "They made the plays and we did not."
Ole Miss had its chances late.
Bost, his team leading, 65-64, missed a 3-pointer with 37 seconds left. Buckner grabbed the rebound, passed to Warren, who hustled past mid-court and called timeout. Nick Williams, with an open look on the wing, air-balled a 3-pointer. State's Kodi Augustus secured the rebound, was immediately fouled, and knocked down two free throws.
The Bulldogs led, 67-64.
"From my vantage point, I thought he had a step-in shot that SEC players need to make," Kennedy said. "He shot it over the goal."
"He had an open shot," Warren said, "he just missed it long."
Warren, for all his heroics, couldn't come up with a last-gasp, game-tying 3-pointer with 12 seconds remaining. Augustus again got the rebound and hit two free throws for the final score.
Warren was one of the few bright spots in a critical loss. Warren broke the all-time school record for 3-pointers made in a career.
But he was oftentimes all alone.
Other than Warren and Graham, no player came close to double-digit points. Steadman Short had eight and 11 rebounds, as he filled in for Reginald Buckner, who had four fouls in 15 minutes.
Three Ole Miss starters -- Terrance Henry, Buckner, Williams -- combined for nine points on 4 of 17 shooting and 12 fouls.
"(Mississippi State) kept fighting," Warren said. "We had our chances where we needed a big play to be made. It wasn't made. We've got to tighten up. We've been in this situation before. We've just got to win some games off."
Ole Miss settled for 3-pointers. The Rebels attempted 35 treys -- the most in school history. Twelve of their 24 made field goals came from long distance. Three players attempted at least five 3s. Warren made 7 of those 12.
The rest of the team was 5 of 21.
"It was a poor effort," Kennedy said.
Ole Miss committed 11 turnovers, while attempting only five free throws. The Rebels attempted 20 more field goals than Mississippi State, but made the same amount (24), good for only 35 percent. "A recipe for disaster," Kennedy said.
They were outrebounded, 38-33.
"It's bad," Kennedy said of being 0-2 in the conference. "We've got to fight. We've got to find a way. Good teams find a way to win in a variety of ways. We were very inept in the second half, offensively."
Ole Miss returns to action Saturday, when it plays host to Georgia at 4 p.m.