Tommy Wright’s men drew the first leg 1-1 in Switzerland without last season’s top scorer but May has shaken off a thigh strain and will return for the second leg at McDiarmid Park, though defender Steven Anderson remains out with a hamstring strain.
Steven MacLean gave St Johnstone a crucial away goal against Luzern and they know a goalless draw back in the Fair City will be good enough to book a third qualifying round date with FC Zestafoni of Georgia or Slovakia’s Spartak Trnava.
Young midfielder Scott Brown believes that despite this advantage, the hosts will still go out looking to attack.
“Having Stevie back is a massive boost,” he said. “Any chance he gets, he usually takes.
“If we can create two or three we should hopefully get a goal.
“Being the home side, the onus will be on us to attack, especially with it being 1-1. A goalless draw will get us through but no-one will want to sit in at home, so I think we will look to get a goal.”
Brown started his third game for the club after filling in for the injured Gary McDonald - who has also shaken off a back injury to declare himself fit - in the first leg draw.
The teenager has vowed to play his part in the Perth club’s bid for the Europa League group stages after having to watch on in envy as his teammates lifted the Scottish Cup back in May.
He said: “I’m feeling better now I have played a few games. Last season I felt like an outsider because I wasn’t playing much.
“I got a game against Celtic towards the end of the season which helped and so has being involved at the start of this season.
“The team did well last year and it’s always great to see the team winning, but I never really felt part of it. The cup final was hard for me to watch because I was desperate to be involved in the team.
“I was delighted for the boys but as much as they tried to get me to join in with the celebrations, I felt a bit left out.
“But that disappointment has stood me in good stead. It’s just made me hungrier to make a difference this year and hopefully I can do that against Luzern.”S
Provisional squad: Mannus, Miller, Mackay, Wright, Easton, Millar, Croft, McDonald, Wotherspoon, May, O’Halloran, Gilchrist, Brown, MacLean, Thomson, Kane, Rodger, Caddis, Banks.