The Warriors take on Ospreys on Friday in the inaugural Magners Leagiue play-offs bidding for a place in the Grand Final.
Al told BBC Sport: "We're not sitting back being happy at being in the semi. We need to go and do ourselves justice and that means playing to the best of our ability. If we do that, we can win.
"The Ospreys are a very good team so it will come down to who plays the best rugby. We want to go and get that win that gets us into the final.
"Although it's not at Firhill, it's great to be in the semis.
"We did what we needed to do (the bonus point win against Scarlets); we went down there and got five points.
"As it turns out, it didn't make any difference but it's good for us as far as momentum is concerned.
"There were things to work on but a lot of good things to take out of the game.
"The Ospreys have played very well, especially over the last three weeks and I know it's going to be a very difficult game.
"They could put out any one of about 35 players and they would be very strong. They are a difficult team to beat.
"They'll get their best team on the park at the weekend and we'll have to be at our very best to win.
"They have a very physical set of forwards. They get good go-forward for their backs so we need to make sure we match that or better that to provide the good ball for our backs.
"We've had good travelling support all season. If we can get a bit of voice down in that stadium it would give the boys a big lift,"