The club knew this cup tie would be tough with the opponents one of the leading lights last year in the EOSFL.
Saints playing up the slope had a worry after two minutes when Rendall went down with what looked like a serious injury.
After a spell of treatment he thankfully recovered.
Lee Wilson was forced to bring off a great save to keep the score sheet blank but two minutes later Smith for the visitors broke through the middle to score a good goal for an early lead.
The visitors soon doubled their tally with good work on the right and Hutchison put the finishing touches to it in front of goal.
On 34 mins Saints had a chance with a free kick from just outside the visitors’ area but Quinn was more than disappointed with his effort as it was taken easily by Swain.
Two mins later a Saints cross saw a Graham shot off target.
Finally some hope came as Michael Fleming played a perfect ball forward, over the visitors’ midfield.
Quinn saw his chance and, despite the last defender’s efforts, managed to flick it past Swain into the far corner of the net.
What looked like hope for the second half, playing down the slope, was not to be when we gave the ball away in midfield.
Brown saw his chance in injury time, lobbed a ball at goal and caught Wilson off his line. Unable to retreat fast enough to get a hand to it, the ball ended up in the back of the net. Disaster for Saints with the visitors going for their break very happy.
It was a disappointing second half for Saints who didn’t really have a decent chance on goal.
On 55 mins Lothian Thistle put the lid on it when a penalty area tackle was adjudged by the referee as a foul. Conor McGregor converted. In the final 12 minutes the visitors broke through several times; fortunately for Saints’ Wilson made three outstanding blocks to avoid the defeat being much worse.
St Andrews Utd: L Wilson, S Macdonald, Rendall, A Macdonald, Ritchie, McInnes, Honeyman, Fleming (Tabengwa 85), Graham, Falconer (J Wilson 54), Quinn (Cunningham 80).