Tomasson has used the example of Yoane Wissa's injury at Isak's former club Newcastle as why they must tread carefully with the Liverpool centre-forward.
"We can't change the situation (with Isak)," Tomasson said. "I'm just happy that Liverpool are doing the same thing I would have done.
"You can see what Newcastle did with Yoane Wissa, who came in instead of Isak. He played international matches with Congo straight away and is now injured. He is still injured.
"That's also a reason why we couldn't play him so much last month. We need a good Isak this month and next month. That's how we plan, while Liverpool have done really well."
Isak still doing preseason
The Dane also said, "One thing I know is that he looks better than a month ago, which is normal. He also made an excellent assist this weekend (against Chelsea).
"I don't know if it's a long way (until he is back to his best), but we're getting closer, as you need six weeks in a pre-season. First you play 45 minutes, then 60 minutes, 75 minutes and 90 minutes. Then you need another three weeks to be at your best. That's normal.
"Whether it will be 90 minutes also depends on the matches, so I can't give a good answer about that. We need to look at the players individually and we get data from the clubs regarding what the players can do physically and whether they can play 90 minutes or not twice.
"He has his own pre-season and plays competitive games. It's a tough way to get fit, but they've handled it well. I think he has done very well. When you come to a new club it is normal that it can take time to interact with the new teammates.
"He is doing his pre-season with competitive matches and I think he and Liverpool have handled it very well. If you look at the way he plays, the way he moves is top class - I still think he is very good."