"We played twice for 120 minutes in six days and spent tremendously, physically and mentally", he said.
They have underachieved in recent years despite boasting a side including Modric, Barcelona midfielder Ivan Rakitic and Juventus striker Mario Mandzukic.
Croatia had also needed spot-kicks to get past a dogged Denmark in the last-16, but Modric insisted they would not be exhausted for the last-four clash against England at Moscow's Luzhniki Stadium on Wednesday.
"If you're asking me a question in a one-off final can we do it?"
Last Saturday, England made the semi-finals with victory over Sweden as action at Wimbledon took place. "We know we have some unbelievable players and a great manager and everyone is clear on what we do".
"We have had events on in camp when some of those guys have been in when the road was named at St George's (Park) after Sir Alf", he said.
Meanwhile, Croatia's Donna Vekic, who was knocked out of Wimbledon by Julia Goerges of Germany in the fourth round on Monday, said she will be sending "good vibes" to her country's football team in Russian Federation.
KL Rahul strikes career-best shot in ICC’s latest T20I rankings
This is Pakistan's ninth successive T20 series win and has helped the team retain their top position in the T20 ranking. Pakistan cricket team thrashed the Australian side by six wickets in the final of the T20I tri-series here on Sunday.
"At this point we will not give up anything and will play against England with all the enthusiasm and passion of Croatian football".
Modric himself is not fussed with the Golden Ball or the World Player award in September, because "the most important thing is Croatia".
"We are a tennis tournament but we are aware that there is something special going on elsewhere".
"We are a sold-out event and there's massive interest".
After such tight matches, it is easy to forget that Croatia produced a feast of attacking play to destroy Lionel Messi's Argentina 3-0 in the group phase. The Croats are licking their wounds after defeating Denmark and Russian Federation in successive shootouts. It also forced England to rethink and make new strategies.
On basis of analytical skills, personal qualities, and command of English, the LOC selected 17,404 volunteers, some of them meant for VIP areas, and trained them to serve in the tournament.
"I've been involved in all of those plans", said Southgate during the pre-match press conference on Tuesday. Hopefully, we can get the win.