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."
Partick expect to have goalkeeper Scott Fox back in contention for Monday's clash after he missed last week's draw against St Johnstone with a foot injury. Stephen O'Donnell has a slight niggle but should also be fine.
Hibernian hope to have Alan Maybury back for the encounter after he missed the club's defeat at Inverness with a knock but Paul Cairney (ankle) is not yet ready.
Hibs midfielder Lewis Stevenson believes the current Easter Road squad is as strong a pool of players as he has ever played in.
Stevenson made his Hibs debut in 2005 and came through the ranks with the likes of Scotland striker Steven Fletcher and just after internationals Scott Brown, Steven Whittaker and Kevin Thomson.
The latter is now back at Hibernian and Stevenson feels the crop of experienced summer signings such as Owain Tudur Jones, James Collins and Paul Heffernan, allied with young players like Alex Harris, can help Hibs enjoy improved fortunes in the Scottish Premiership this season.
The 25-year-old said: "I have been ever-present this season and it would be nice to keep that going but we have got a strong squad and things can change, players are coming back from injuries and everyone needs to be on their toes.
"I honestly think we've got as strong a squad as we have had since I've been here.
"When I first came there were a lot of players who went on to play in England and play for the Old Firm.
"That was probably the best squad I have played with but I see a lot of players here with a lot of ability and young boys with a lot of potential so I don't see why we can't kick on and be as good as we were then."
Hibs have recovered from a poor start to the season when they shipped nine goals against Malmo in the Europa League before losing their first two league games, although a six-match unbeaten run came to an abrupt halt at Inverness last weekend.
Stevenson said: "A lot of players came in in the summer and it maybe took us a bit of time to gel.
"I was never worried it wasn't going to happen after the first two games. Even the Motherwell and Hearts games could have gone either way.
"I thought the manager was getting a lot of unneeded pressure. We are all going in the right direction and everyone was behind him so it's nice that we turned it round for him.
"The players and people behind the scenes know he is doing a good job."
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- Scottish Premiership