England's Jagielka set to win World Cup fitness fight
Jagielka struggled to recover from a hamstring injury suffered in February, raising doubts about the Everton centre-back's ability to get back to full fitness in time for the tournament in Brazil.
The 31-year-old, who is expected to partner Gary Cahill at the heart of England's defence, was sidelined for two months towards the end of the Premier League campaign, but returned for the final two matches and is now nearing full fitness after an intense week-long training camp with England in Portugal.
"Last week was important for me to get a few more sessions under my belt," Jagielka said on Tuesday.
"We had a really good session today and it is about getting myself ready.
"I do not need to be 100 per cent fit this week, it is more about building up and getting match practice before we go out to Miami for the friendly matches.
"Hopefully I will time it perfectly for the opening group game."
Many perceive England's defence to be their weak spot due to a lack of star names, but Roy Hodgson's team conceded just four goals in qualifying for the World Cup.
Hodgson will also be comforted going to Brazil knowing that England have not lost a game when Cahill and Jagielka have started together.
That statistic has meant Jagielka is now integral to Hodgson's plans, unlike two years ago when he was an unused squad player in Euro 2012.
Jagielka thinks his game has come on a lot since then, partly due to the fact that he was named Everton skipper at the start of last season.
"Being made Everton captain this year forced that on me a little bit more," said Jagielka, who started seven World Cup qualifiers.
"I am quite loud and vocal on the pitch. It is important we have leaders in all different types of areas.
"I am not guaranteed to play but I am in a better position than I was two years ago. I have played a decent role in the qualifying campaign to get us to Brazil and it would be nice to get some game time and be part of a successful England team."