The midfielder was just 17 when he made his debut for Chelsea in the Champions League four years ago.
After 17 appearances in Carlo Ancelotti's team in the 2010-11 season, expectation was high for McEachran's future both in west London and with the Three Lions.
However, when Ancelotti was sacked at the end of that campaign after failing to replicate the double-winning exploits of the previous season, McEachran's progress was halted and, like many Chelsea youngsters before and after him, he found the route to the first XI blocked at Stamford Bridge.
Loan spells at Swansea, Middlesbrough and Watford have followed and the career of McEachran, still only 20 and a fixture in England's Under-21 set-up, has threatened to wane before it has even really started.
Rosler this week offered McEachran a chance to reinvigorate himself at the DW Stadium for the rest of the season, though, and the fact the player will give up money to do so sits well with the German.
Rosler said: "Because of his outstanding qualities as a footballer - and the fact that he played for such a world-class team for 17 games in a season - the expectation on him was far too high to fully fulfil that week in, week out.
"They sent him out on loan and for some reason his career has stalled a little bit. He didn't progress as much as Josh and maybe Chelsea thought. Now, Josh comes into a situation here and Josh knows exactly what he needs, which way he will respond best and Chelsea also know that."
For all of his qualities Jose Mourinho is not renowned as a great developer of youth players, but Rosler believes he has been entrusted with the task of moulding McEachran because of the work he did at former club Brentford in educating George Saville, another Blues youngster.
Midfielder Saville is still with the Bees on a loan basis, and Rosler added: "George went in a very good direction and we felt we can maybe do the same thing for Josh.
"The main thing for Josh now is to bring himself on the level that he can really compete for 90 minutes and that is what we'll try to do."
Rosler has frequently spoken about how Manchester United loanee Nick Powell's stay with Wigan will ensure he returns to Old Trafford ready to become a key cog in a top Premier League side, and he has no doubts McEachran can tread a similar path.
The German manager said: "Josh is a confident lad; he knows that he' a good footballer. He knows that he can play at his best in the Premier League, no problem.
"But at the moment, Josh is not at his best so we have to make sure he recovers form, he recovers confidence and he is capable of performing consistently at a high tempo in the modern way of football, and that is what Chelsea are looking for for their players. When a player sacrifices part of his wage, that is a great starting point."
McEachran is not up to speed yet and will not play in the FA Cup against Crystal Palace on Saturday as Wigan look to continue their defence of the title they won back in May.
They may have to do without central defender Ivan Ramis too, after Rosler revealed Wigan had accepted a bid from Cardiff on Friday afternoon, and Powell is only fit enough to start on the bench.
Nevertheless, the Latics boss does not think victory over Tony Pulis' side would constitute a shock.
"We are at home and we want to go further," he said.
"We know we can win games, we have shown that since I came to the club.
"I say this even when we play Crystal Palace - a Premier League side - it's up to us, are we winning or not. We have the quality in our team to leave the 90 minutes as a winner."