"That's the great thing about hockey," said Auld. "All the players know what different players go through and how tough it can be when you get bounced around.
Auld finished with 25 saves, allowing only Jason Blake's goal.
"Everyone has been so welcoming. I didn't know many guys on this team but everyone has made me feel right at home, and that's great."
Vesa Toskala played well for the Maple Leafs, making 18 saves in the loss.
The checking was so tight that each team recorded only one shot during the first 10 minutes.
"They're a very defensive hockey team," said Toskala. "They just sit back and wait for those turnovers. There were long periods where I didn't touch the puck."
Blake took Toronto's second shot and beat Auld on the short side at 10:28 with a wrist shot from the middle of the circle to the goalie's right. It was Blake's fourth of the season.
"It's obviously frustrating," Blake said of the loss. "We had some chances but (Auld) played great.
"We can't let this loss linger too long. We've got a tough game against Tampa Bay on Monday night, and we've just got to get right back at it."
Boston tied it with a power-play goal at 12:25. Pavel Kubina was penalized for hooking, and Kobasew took a wrist shot from the middle of Toronto's zone that whistled through Toskala's legs for his 12th.
It was back to grind-it-out hockey after the brief offensive surge. Every time a Leafs player touched the puck, a Bruins defender was all over him.
"We knew what to expect," Maple Leafs center Kyle Wellwood said. "They'd beaten us twice already playing that style, so we were really focused on beating them.
Wideman gave Boston a 2-1 lead at 9:25 of the second period with a low slap shot from the blue line that glanced off a stick on its path to the net.
Toronto could have tied the game if its power play had been clicking. Andrew Alberts was sent off for tripping at 6:45 of the third period, but the Leafs were unable to get anything going. When Glen Murray took an interference penalty at 14:22 and a tripping penalty at 19:13, Toronto still couldn't take advantage.
The Leafs entered the game ranked third from the bottom in the NHL on man-advantages.
Mats Sundin's club-record point streak at home from the start of a season ended at 16 games.
Darcy Tucker was back in the lineup after sitting out Toronto's 6-2 win over the Rangers in New York on Thursday with a sore shoulder, but he remained ineffective.
- Toronto finished 0-for-6 on the power play. Boston went 1-for-4.
- Toronto lost its two previous games against Boston this season and hasn't beaten the Bruins since last Jan. 4.
- Nik Antropov's natural hat trick in the win in New York was the first by a Leafs player since Sundin did it November 1998.