To be fair it's not just Saints who are being hit with longterm injuries. Probably doesn't help with playing 2 matches in the space of a few days. Hull KR have lost Ryan Shaw for the season with a knee injury too.
Tommy will be missed but it's an opportunity for someone else to step up and make a name for themselves. He's been fairly solid but very unspectacular this season and is probably less of a loss to the team than he was when he broke his leg last season.