Ian Murray, the St Mirren manager, hopes to get an answer by the end of the week from transfer target Andy Webster.

The former Scotland defender has been training with the Paisley club, who are keen to sign him. However, with right-back Jason Naismith's serious knee ligament injury having put diminished the Buddies' defensive options further, Murray admits his old Rangers colleague will have to make up his mind soon so he can focus on completing his transfer business.

"Webby's been training with us for over a week so we're looking to get something sorted one way or another with Andy over the next day or two," said the manager. "The injury to Jason changes things because we now also need to source a right-back, which isn't going to be easy. If it's a yes, then we've probably still got scope to sign him, but if it's a 'no', then we need to move on and look at other people."

Naismith, 21, has been ruled out for six months after suffering ligament damage in Saturday's defeat to Dumbarton. Murray added: "We feared at the time that Jason had taken a bad one. It's a blow for the team and for Jason. He's got a strong character but we need to look after him. The one positive is that he's got time on his side to bounce back."

Murray insists Mark Ridgers will keep the gloves for tomorrow's Renfrewshire derby at Morton even though new goalkeeper Jamie Langfield made an impressive debut in Tuesday's Petrofac Cup win over Annan.

The manager said: "Langers did great. He's vocal and he's a great signing for us. He's not played a lot of football recently but you could see against Annan the quality he brings. He made a fantastic save and his distribution and the way he thinks about the game was there for all to see. He's here to put Mark under pressure and if he keeps up the level he showed the other night, then Mark will need to rise again.

"Mark's done nothing wrong, we just felt Tuesday was ideal for Jamie got a shot. I've noticed Mark upping his game since Jamie's come in and that's what you want. There might come a time when we need to make a change - like any position on the park - but at the moment Mark's done nothing to merit not playing."

Meanwhile Buddies youngster Jordan Stewart hopes to play a part in tomorrow's Renfrewshire derby after marking his first start with a goal. The 19-year-old left-back was thrown in against Annan as Murray made seven changes and the manager admitted afterwards that Stewart was one of the fringe men to catch his eye after he netted his side's equaliser in a hard-fought 2-1 win at Galabank.

Now the Ralston academy product, who had made only one sub appearance before, is hoping he's done enough to be pitched on to the Cappielow cauldron tomorrow night. "To get my first senior goal in my first start is unbelievable," he said. "I've only had one sub appearance and a few friendlies before. I've been close to getting in for a while but with the run of games we've got coming up, the gaffer decided to rotate the squad a wee bit and I got my chance against Annan.

"Getting the goal has given me loads of confidence so hopefully I can push on and take my chance if I can stay in the team. Hopefully I can play a part on Friday night. It's a huge game and we're all looking forward to it. I've never played against Morton in a competitive game."

Stewart, who has been with St Mirren for a decade, admits he'd love to follow in the footsteps of Kenny McLean and John McGinn, who earned moves to Aberdeen and Hibs respectively after coming through the Buddies' youth ranks. "The club tries to push as many young boys through as possible so it's a good place to be," said Stewart. "It gives you a real incentive when you see boys like Kenny McLean, John McGinn, Jason Naismith and Sean Kelly getting into the team and doing well. I was in the 20s with all those boys so it inspires you to know it could be your turn next."