Yeah it's mostly based on form.
Colsaerts has basically been playing terrible golf since mid April. In his last 10 starts worldwide, he has made only three cuts and his best finish was a t59 in early June where he still finished 15 back of the winner. In that time, he has only three rounds in the 60s. This week, I'm thinking the winner will be somewhere double digits under par.
This is a new course for everyone and is pretty long at almost 7500 yards. Fairly wide fairways but the rough is some links style. It also has big greens. So distance and putting should be key. Obviously Colsaerts I'd a bomber so no problem there. However, he's 180th on Euro tour in putting.
Karlberg has been trending in the right direction. He has four top 15s in his last six starts, including a t9 last week in Denmark. He's a big enough hitter, almost 291 off the tee, where the length this week should cause any issues. He's 21st on tour in stroke average, so he's been making birdies. And best of all, he's top 25 on tour in putting, including 14th in putts per round.
Hope this is helpful.