Modric turned 41 at the start of September and scored on his 203rd international cap as Croatia opened up their Nations League campaign with a 2-1 win in Czechia.
The AC Milan playmaker has remained openminded over his plans with Croatia as he looks to go step-by-step for club and country.
Ahead of facing world champions Spain, Suker has hinted at Modric being ready to keep on going for at least a few more months.
"Modric has shown he can still perform at the top level. We have incredible quality in the squad. Hopefully there will be goals against Spain, because I don't like 0-0s.
"Spain are favourites, but as a Croatian, I want to win. They have an amazing team, a good manager, and ambition. Hopefully they relax, but whenever people underestimate us, we step up."