A night of celebration ended with a banner raised along with fears as the star goalie was sent to the doctor after being struck in the right eye by the stick of Pittsburgh Penguins captain Sidney Crosby.
Arbour came back to the Islanders one more time to coach the team he guided to four straight Stanley Cup championships in the 1980s for a 1,500th time in the regular season.
Miroslav Satan scored the tying and winning goals in the third period of New York's 3-2 victory over the Penguins.
"We had a bad five minutes in the second period, but otherwise, we played really, really hard," the 75-year-old coach said. "I talked a little bit, not a lot. It was nothing spectacular. I bit my tongue a little bit."
It would've been perfect if not for the injury to DiPietro, in the second season of a landmark 15-year contract with the Islanders. Team spokesman Chris Botta said initial reports showed the injury wasn't serious, and that the 26-year-old DiPietro was sent for an evaluation to confirm that diagnosis.
"I just asked him how he was and he said he was all right," captain Bill Guerin said.
Arbour was invited behind the bench to coach the team again and earned Islanders win No. 740 behind the heroics of Satan, who netted the winner with only 2:41 left when he put in a rebound of Marc-Andre Bergeron's shot.
"When we came back to the bench you saw a legend standing there," Satan said. "We knew we only had one chance to win the game for him."
Arbour retired after the Islanders were swept in the first round of the 1994 playoffs by the New York Rangers, but now he can leave on a winning note.
On his return he didn't move more than a few steps away from his spot to the left of regular coach Ted Nolan, whose idea it was to have Arbour return.
"Just by him being here won the game," Nolan said. "Al said he didn't know all the names of the players, but they sure knew him."
No one has coached or won more games with one team than Arbour. He left the second time when Crosby was less than 7 years old. A banner commemorating his 739 previous Islanders wins was lowered after the game, replaced by one with his name and 1500 as streamers and confetti were shot from the rafters.
"I was very surprised at the end," he said.
Arbour held a lineup card in his left hand throughout and raised both arms in jubilation when Satan erased the remnants of a two-goal deficit 5:30 into the third period. Nolan did a spin and leap of his own.
That was nothing compared to how the whole bench jumped when Satan put the Islanders in front.
"It feels very good but I really didn't do that much," Arbour said. "It was all the players and coach Ted Nolan."
Trent Hunter got New York within 2-1 midway through the second after Ryan Malone and rookie Tyler Kennedy built the advantage for the Penguins, 1-2 on a four-game road trip.
Crosby assisted on Malone's goal to stretch his point streak to a career-best 12 games and then drew the ire of the sold-out Nassau Coliseum crowd when he struck DiPietro in the mask with his stick in the second period.
Crosby got four minutes for high-sticking. DiPietro, who had already left for the dressing room, was called back down the tunnel to show the referee he had been cut near the eye before retreating again.
Wade Dubielewicz was perfect in relief.
The Islanders couldn't convert then or on any of their six power-play chances.
Malone made sure the Penguins netted a man-advantage goal for the 13th straight game, every one they've played. Crosby went without a point in Pittsburgh's season-opening loss at Carolina, but hasn't been shut down since.
Malone has 12 career goals in 19 games against the Islanders - his most against any team. Both of Malone's NHL hat tricks came last season in games with the Islanders, as did his first goal in the league - scored in 2003.
After a straightforward first period, things turned strange.
Less than two minutes into the second, Kennedy - in his fourth NHL game since being called up last week - ripped a shot that appeared to sail into the top left corner behind DiPietro, but it was waved off by referee Eric Furlatt.
Gary Roberts threw his hands up in celebration with the rest of his Pittsburgh teammates, but play continued for another 1:51 until the next stoppage. Video replay confirmed Kennedy's first career goal and gave the Penguins a 2-0 lead.
New York allowed eight Pittsburgh shots before recording its first of the period at 5:10. That was enough to jump-start the Islanders.
On a wraparound by the Penguins, the puck took a funny hop and caromed back in front to Hunter, alone in the slot for a quick shot that cut New York's deficit to 2-1 at 8:20.
DiPietro didn't return after his injury and finished with 16 saves on 18 shots. Dubielewicz stopped all seven he faced for his first win of the season
Marc-Andre Fleury made his first appearance on Pittsburgh's trip and stopped 36 shots. Dany Sabourin beat Minnesota in the opener, but couldn't protect a two-goal lead at Colorado on Thursday in Pittsburgh's 3-2 loss.
"We had the lead the last couple of games and we let it slide," Crosby said. "We can't keep coughing it up, especially when we were going back and forth.
"We played hard to get the lead, and tried to keep it, but just couldn't."
Notes: Former Islanders general manager Bill Torrey, who hired Arbour, dropped the ceremonial first puck with Scotty Bowman, the only man with more NHL coaching victories than Arbour's 782. ... The Penguins scored a power-play goal in the first 14 games of the 1988-89 season. ... Crosby had 17 points (3 goals, 14 assists) in seven games against the Islanders last season. ... Malone has more points (17) versus New York than any other opponent.