Northern Ireland manager Nigel Worthington received a boost when Jonny Evans joined the squad in training today.
The Manchester United defender has been troubled by an ankle injury and sat out the victory against Arsenal at the weekend.
The problem also caused him to miss Northern Ireland's draw with Israel in a friendly at Windsor Park last month.
Evans joined the group at Antrim's Greenmount College as they began their preparations for the vital World Cup qualifier against Poland in Chorzow on Saturday.
Worthington will be hoping the 21-year-old, who has already won 17 caps, will remain injury-free.
Northern Ireland are looking to compete the double over Poland after a 3-2 victory in Belfast in March.