The midfielder came through the youth ranks at Easter Road but failed to make a first team appearance before his departure in May 2012.
The 23-year-old felt there were doubts over his ability during his time at the Edinburgh club but he insists he has shown he is good enough to play in the Scottish Premiership.
"It will be a good moment," said the Partick skipper, who penned a 12-month contract extension in August.
"It's good that the gaffer has made me captain here and I'm looking forward to walking out against the former club that didn't have faith in me and thought I couldn't do this.
"I'm here to prove everyone wrong. I've done it so far and hopefully I can keep going.
"People doubted me at that club and didn't trust me but I've shown that I'm good enough and I'm here now.
"I always believed in myself and knew I could be here. I've just got to believe in myself again and play the way I can."
Welsh says he never once doubted his own ability despite others not showing the same faith in him.
He said: "I always believed in myself. I knew I was good enough.
"I could see some players playing who I thought I could do better than.
"But that's down to a manager's opinion.
"I voiced my opinion to a few managers there but it's their choice who they put on that park and I wasn't given the chance.
"They didn't think I was good enough or didn't trust me but that's their opinion and I'm past that.
"I'm here and I'm happy and I'm showing everyone that I can play at this level and that's all that matters to me."
Welsh is now determined to repay the faith shown in him by Thistle boss Alan Archibald by continuing to impress on the pitch.
He said: "It gives you the confidence to show what you can do if someone believes in you.
"The gaffer and Thistle have shown a lot of belief in me so I'm just trying to reward them for doing that for me."
Hibs struggled at the start of the season but had embarked on a decent run before last weekend's defeat to Inverness.
Welsh said: "It's been a mixed season for Hibs.
"They had a tough start and there was a bit of pressure on the manager but they have turned it around, as everyone has seen.
"They've had a few good wins and they had a hard game against Inverness, who are flying this season.
"They will be looking to get another win this week and we will be looking for the win just as much as them."