Udrih, who was filling in for Orlando point guard Jameer Nelson (sprained ankle), led the Magic with 20 points and eight assists.
Orlando also was missing leading scorer Arron Afflalo (strained right hamstring), but center Nikola Vucevic had 17 points and 15 rebounds in his first game after missing five because of illness and concussion.
The Magic were competitive while Maurice Harkless scored 17, and D-League veteran Tobias Harris added 11 points and 10 rebounds.
Harris, though, was harassed chiefly by Smith into a 5-for-18 shooting night. Orlando also struggled at the free throw line on a 16-for-27 (59.3 percent) while losing for the 11th time in 13 games.
"(Smith) has great length and athleticism," said Orlando coach Jacque Vaughn. "The Hawks have big, strong, physical guys that make it tough to score on them. If it's not Horford or Pachulia, then it's Ivan Johnson.
"We're putting together quarters, we're putting together halves. That will eventually add up to putting together games and consecutive games."
Atlanta grew its lead to 14 points on a three-point play by Johnson with 7:14 left in the game.
NOTES: Atlanta's Kyle Korver made a 3-pointer in the second quarter, the 67th straight game in which he's hit at least one trey. The former Creighton star is one game from tying Reggie Miller (68) for the fourth-longest such streak in NBA history. Only Dana Barros (89), Michael Adams (79) and Dennis Scott (78) put together longer runs than Miller. ... The Hawks were also missing guard-forward DeShawn Stevenson (knees). He was unavailable because he doesn't play in back-to-back nights. ... Atlanta is already without guard Louis Williams, who suffered a season-ending knee injury a couple months ago, and the Magic have been without second-leading scorer Glen Davis (fractured foot) for two months.