AMHERST — Heartbreak struck the UMass men’s basketball team for the second time in three games on Tuesday night at the Mullins Center.

Clinging to a one-point lead with 12.5 seconds left after Rahsool Diggins’ acrobatic layup put the Minutemen ahead, Saint Joseph’s guard Lynn Greer III drove hard to the cup through contact and put up a floater. After his initial attempt rimmed out, Greer III grabbed his own rebound and put it back up and in from point-blank range to give the Hawks a 78-77 lead with a little over a second to go.

Diggins chucked a last-second attempt wide left as the buzzer sounded, handing UMass an eerily similar loss to the one at Loyola Chicago just six days ago.

The defeat was the Minutemen’s first on their home floor in conference play (now 3-1).

“Yeah, it actually feels exactly the same [as the Loyola game],” Diggins said. “It’s a sour taste in our mouth right now, but we’ll get back to practice and focus on rebounding specifically... I’m good at moving forward, because there’s always a next one. You just gotta push forward.”

After Diggins’ go-ahead bucket, UMass head coach Frank Martin burned his final timeout to discuss his team’s defensive strategy for Saint Joseph’s final possession. Martin told the team that if nobody could grab the rebound, to at least swat it out of harm’s way underneath the hoop.

Neither of those happened.

“‘Get a stop, and if you can’t rebound, punch the ball,’” Diggins said of his coach’s message in the huddle. “We had no timeouts, so if they score, get it out and push it.”

Saint Joseph’s went on two game-changing spurts in the second half thanks to UMass’ inability to take care of the ball. Ten of its 17 turnovers – the most UMass has had in a game since Dec. 2 – came over the final 20 minutes.

A 12-1 Hawks run from the 10-minute mark to the 5:45 mark cut the Minutemen’s 13-point lead down to two. During that stretch, UMass had no field goals and four turnovers. Then, after consecutive buckets from Josh Cohen and Keon Thompson, another dry spell struck.

The Minutemen didn’t score again from 5:20 down to 1:30, having no field goals and four turnovers in similar fashion. Several trips down the floor, UMass sloppily dribbled the ball into Hawks defenders, and it led to easy layups in transition. Saint Joseph’s had 21 points off turnovers.

“Too many turnovers,” Martin said. “We took that lead, and we probably had seven consecutive of our worst offensive possessions we had all year. Guys fumbling the ball, and they weren’t aggressive plays, they were just give them the ball and let them go shoot layups. Once they got back in the game, it was a rock fight until the end.”

Nobody on the floor for UMass had an answer for Hawks guard Erik Reynolds II. The junior cashed in two 3s in the game’s first minute – a sign of things to come. He had 30 points on 10-for-16 shooting, including 5-for-7 from long distance. Reynolds II was Martin’s biggest concern on the defensive end coming in,  and his full skill set on display showed exactly why.

“We had no answer for Erik Reynolds,” Martin said.

The Minutemen’s calling card all season has been their relentless aggression on the offensive glass. Their 12 boards on that end led to 20 second-chance  points, and it’s no coincidence that their dominance continued in Matt Cross’ return to the lineup after missing three games with an ankle and tooth injury.

UMass went on a 9-0 run to take a 57-48 lead, and it was capped by Cross making several hustle plays. He grabbed two offensive boards in a row and kicked it out to Diggins, who side-stepped into an open 3 and buried it to give UMass its largest lead of the night at the time.

The next basket, Cross led a fast break and finished it with a slick bounce pass in stride to Jayden Ndjigue for an easy layup. After that, however, it was all Hawks until the final horn. Cross showed signs of his old self, but even Martin noticed glimpses of timidness – which is expected after missing three straight games in the middle of conference play.

“He was hesitant to shoot the ball, which is what happens when you don’t play for three weeks, but without him, we’re in deep trouble today,” Martin said. “Thank god he was willing to strap it up and go today.”

Diggins, a Philadelphia native, was the team’s leading scorer again with 17 points. Daniel Hankins-Sanford tossed in a career-high 16 points to go along with six boards, and Cross finished with 12 points and 9 rebounds. Thompson chipped in 10 and four assists as the fourth Minutemen player in double figures.

Saint Joseph’s scored at will at the rim, and the Hawks probably should have had at least five more field goals in the paint if it weren’t for several shots going halfway down and back out. Tuesday was probably the worst UMass’ defense has looked in conference play – the game against Rhode Island being the only argument.

“All they did was shoot layups,” Martin said. “All they did was take the ball, drive it and go shoot layups. The guy guarding the ball was no good, our help defense was no good. Then we played with a little spunk, built our lead, then went right back to the nonsense – getting outran down the court, guys not getting back on defense. We haven’t done that all year. I got no idea. I wasn’t in the mood to have a conversation with my team after the game. We’ll figure that out tomorrow.”

UMass (12-7, 3-4 A-10) heads to Saint Louis on Saturday for an 8 p.m. ET tip with the Billikens.