MIAMI – Their playoff opportunity growing so small with each passing loss they can barely still see it, the Timberwolves lost 123-105 at Miami on Friday, and their hard-driving coach demanded more of his young stars and promised he will push them and their teammates hard through the regular season's final 14 games.

"It's a long season, and it's a long season for every team in this league," Wolves coach Tom Thibodeau said. "You have to have the mental toughness to get through and endure and when things aren't going your way, you can't cave in. We have to change our mind-set and I have to drive. There's not going to be a letup. We have to practice better. That's on me."

The Wolves now trail Denver for the Western Conference's eighth and final playoff spot by five games and time is ticking loudly.

Thibodeau's team won seven of 10 games recently after they held opponents to 91 points or fewer in the first five victories. They've now lost three of their past four games, and allowed Boston 117 points on Wednesday and the Heat 123 points — including 33 in the fourth quarter alone — on nearly 59 percent shooting on Friday.

Afterward, Thibodeau declared, "This isn't AAU basketball. This is get-out-there and everyone has to do a job together."

The Wolves didn't come nearly close enough to doing that job in their first game without injured reserve forward Nemanja Bjelica, whose season ended Wednesday in Boston when he injured his left foot.

The Wolves never led. They surrendered a 10-2 run late in the second quarter that sent the Heat into halftime with a 15-point lead. They trailed by three points three times midway through the third quarter and after falling behind by double digits again, they drew within five points twice, with as little as 7:20 left in the game.

But a Heat team that has mined free agency for such players as Tyler Johnson (23 points) and Hassan Whiteside (23 points, 14 rebounds) scored 14 of the game's next 16 points to win resoundingly. After starting the season just 11-30, Miami won for the 23rd time in 28 games.

Thibodeau lamented his team's rebounding, intensity and its readiness to play.

"That's part of my job, I have to have them ready so we've got to change," he said. "We moved forward when we were playing great defense and with great intensity and so our leaders have to lead. They have to play defense. There are a lot of guys who can get stats and lose. That's meaningless. It's the winning that's important and the intensity and the preparation that goes into it so you can play well. It takes maximum effort and maximum concentration."

One of his team's young leaders, Wolves forward Andrew Wiggins, had one word to describe his team's defense.

"Terrible," he said. "If a team shoots 60 percent, that's not good. We've got to step it up. In practice, go over what we did and fix it. We've just got to help each other on defense, be fastened together."

When asked how responsible he felt for Friday's performance or lack thereof, Wiggins said, "A lot. It starts with me and [second-year center Karl-Anthony Towns]. If we go hard from the jump and guys see that we're getting stops, everyone follows."

Towns said after the game that his shoulders are wide.

"At the end of the day, when you lose, you have to take the blame," he said. "When you win, you can't take any of the glory. I'm more than willing to take the blame. That's just the way it is. It starts with us: Me, Wig, Ricky [Rubio] and all the starters, we've got come out together. At first you look at yourself. I've got to do more. I've got to find a way to do more. I want to be in the playoffs this year."