The Jambos are seeking their first victory since manager John McGlynn parted company with the club last week, with first-team coach Gary Locke being placed in interim charge of team affairs.
The Edinburgh outfit will be looking for a positive result following the weekend defeat to Motherwell, with players also keen to stake a claim ahead of the Scottish Communities League Cup final against St Mirren later this month.
But Saints - sitting fifth in the table - are keen to pick up the wins that will secure their spot in the top half of the table before the league split.
Lomas said: "Gary Locke is a very respected former player and coach. He's a great lad and I'm sure the lads will want to play for him.
"They've got a cup final coming up and maybe some of the more experienced boys have got a point to prove. There are various reasons why they'll want to do well but we can only focus on what we can do.
"We can only focus on our performance, our defending and our attacking. It's a great opportunity for us but it's never easy to go to Tynecastle. It's a tough venue and we will have to perform."
He added: "The league's so tight and I think that's been a positive this year that everybody can beat everybody.
"Everybody has to perform because everybody can beat anybody on the day. If you don't perform in the 90 minutes, you get beat. It's as simple as that."