West Brom boss Slaven Bilic insisted his side must handle the promotion pressure after a 4-2 win over Hull kept the title heat on Leeds.
Hegazi was sent off in stoppage time after his second yellow card, but Albion moved closer to ending their two-year Premier League exile.
Kevin Stewart and Mallik Wilks twice levelled for struggling Hull, who sit a point above the relegation zone.
In contrast, Albion are now five points clear of third-placed Brentford with five games left in the title run-in.
Bilic said: "The teams who are below us, Brentford, Fulham and Forest are doing well but they are hoping.
"We have to cope with the pressure. We wouldn't swap with them and we have to cope with it. The pressure will only get bigger. It doesn't mean we would swap with them.
"We have to continue being brave and relax in a positive way. Today was a game to enjoy.
"It was a very frantic match, the stage is frantic. It was a very open game, we didn't want it to be open when they were getting the ball.
"On the ball we were excellent but they put us under pressure with a very simple way of football. We were a little afraid they were going to hurt us.
"We are back on track and I'm really pleased with that."
Austin opened the scoring from close range after four minutes, but Stewart's deflected drive levelled 20 minutes later.
Hegazi's header made it 2-1 only for Wilks to equalise again three minutes after the break.
But Grosicki restored Albion's lead against the club he left in January just 76 seconds later. Diangana struck a fourth 14 minutes from time and, despite losing Hegazi to a second yellow card in injury time, the hosts held on.
Hull spurned several chances at 3-2, with Wilks and Jon Toral going close, and boss Grant McCann criticised his side's defending.
He said: "I think some of the goals are unacceptable. The first one we tried to bring it down rather than head, we switched off for the third and the fourth was a sucker punch. In an attacking sense we were excellent.
"The second goal was the worst. Jordy (De Wijs) knows himself, he made a mistake and hopefully he doesn't make any more.
"We've worked hard on attacking set-pieces. We're seeing benefits of that. Every ball (George) Honeyman put in we were so close. The work has gone in and we're looking better defending and attacking set plays."