With roster positions on the Heat at a premium, rookie free agents Terrel Harris and Derrick Byars recognize the tight window to earn a spot is about to close.

Harris and Byars had solid performances Sunday in the Heat’s 118-85 exhibition victory over the Orlando Magic and hope to follow with similar production when Miami concludes its abbreviated preseason schedule Wednesday in a return game at Orlando.

The turnaround time between the two exhibitions is short, as are the days leading to the Heat’s regular-season opener Sunday at the defending champion Dallas Mavericks. Harris and Byars soon will know whether this will be another shattered NBA opportunity or they have made a roster headed by marquee players Dwyane Wade, LeBron James and Chris Bosh.

“There’s a lot on the line but you don’t want to put too much pressure on yourself,” Harris said after Tuesday’s practice at AmericanAirlines Arena. “You just want to go out and play your game and show the coaches what you can do — just like the first game.”

Harris showed plenty to Heat brass Sunday. The 6-5 guard from Oklahoma State scored 16 points on 5-of-7 shooting, including 4 of 5 from three-point range.

“I just stayed within myself,” Harris said. “[Orlando] really didn’t know too much about me. It’s going to be different next game because they’ll have somewhat of a game plan against me. I have to just keep playing well and pick up my intensity a little bit.”

Harris, 24, was undrafted in 2009 and has spent the past two years playing overseas and in the NBA Development League. Although not fortunate to participate in a longer training camp, Harris still finds advantages in the shorter preseason.

“If you’re not a [draft] pick, some of it is time, place and luck,” Harris said. “To come from the D-League, not knowing where I was going to be this summer, to the lockout, to playing with some of the best players in the league, it’s a blessing.”

Byars also gave the Heat reason for an additional look. In 13 minutes Sunday, Byars scored 12 points on 5-of-6 shooting.

Like Harris, Byars, 27, has experience overseas and in the D-League. The 6-7 guard/forward from Vanderbilt also was part of the Philadelphia 76ers’ training camp in 2007 but failed to make the roster.

“I know there’s not much room left but I just want to work as hard as I can and get as much as I can from a team with great superstars and great veterans,” Byars said. “If I get some time on the court, I just want to maximize it in the minutes I play — whether it’s two minutes or 20.”

Harris values his previous NBA training camp experience as well as his D-League stop in Bakersfield, Calif., and two years of playing in France and Germany.

“There is no pressure for me,” said Byars, who also participated in summer league teams with the New Orleans Hornets and Orlando Magic. “I’ve been in this situation before in several other camps.”

Heat veteran forward Udonis Haslem sympathizes with Harris and Byars. Haslem was in a similar situation when he joined the Heat as an undrafted free agent in 2003. Haslem capitalized from his first training camp with the Heat and is now one of the team’s stalwarts in his ninth NBA season.

“I remember the situation I was in; I took advantage of it with a longer training camp,” Haslem said. “Unfortunately, these guys have a shorter period of time but I don’t think they’ve missed a beat. They have competed at the highest level.

“These guys can make the team. It’s going to be a tough decision. I’m rooting for all these guys, whether they stay here or somewhere else.”

Elsewhere

• Heat coach Erik Spoelstra said center Eddy Curry (left hip flexor) and forward Shane Battier (left quadriceps) missed Tuesday’s practice and appear doubtful for Wednesday’s exhibition at Orlando.

Although both players did not practice with the team, they worked on conditioning.

“We are increasing their workload,” Spoelstra said. “They are making progress. We are thinking big picture so we are not in a rush or in a panic mode. We have time to make sure they are healthy enough to build the workload.”

• Spearheaded by team president Pat Riley, the Heat is sponsoring 250 holiday care packages that will be sent by America’s Moms for Soldiers to U.S. troops in Afghanistan

who have minimal correspondence from home.

Riley has been an avid supporter of matters related to U.S. troops.

“I know Pat really cares about the military,” Bosh said. “It’s near and dear to his heart.

“If you really think about it there are so many situations where there has to be an awareness to it. Some of our troops come home to nothing. To think about someone who has defended his country with his life. Who has put himself in harm’s way to protect our freedoms.”

For additional information, visit www.americasmomsforsoldiers.com.