The 34-year-old forward, who has won 33 caps for Iceland, arrived at Glasgow Airport with his team-mates yesterday afternoon and wasted no time in spelling out their gameplan for tomorrow night's encounter.
Gunnarsson impressed McCall when coming off the bench during Stjarnan's 4-0 away win over Bangor City last week, a result that completed an 8-0 aggregate victory, but he concedes his side will be considerably more cautious this time round.
"We are going for a good result in Scotland to have a chance in our home game," he stated. "We are going to be packed defensively. Our priority is not to let them score."
Stjarnan currently sit second in the Icelandic Urvalsdeild, two points behind FH Hafnarfjordur, after 11 matches. Gunnarsson scored a late equaliser in a 2-2 draw with FH on Sunday and believes the fact his side are well into their domestic season will give them a vital edge over Motherwell.
"We are in top shape," he said. "The season starts soon in Scotland and they are probably in good shape, but we have played more games than them. We should be fitter than them, but we will see.
"I hope they don't know too much about us and we can surprise them a little bit, but they have probably done their research. It is an honour to reach the second qualifying round and play a good team such as Motherwell."