Player(s) Value Decreasing?

I started a new game at Leyton Orient, and had this young keeper Jones or something, 20yrs old. He was similar in stats to my 25yr old keeper, so thought I'd play the younger lad in the hope that he would become our solid number 1 for years to come and go on to become a decent keeper given time. I have just finished the 1st season and he was an ever present. At the start of the season he was worth 70k, but the longer the season went on his value reached a peak of £120k. His stats didn't improve greatly, but very slowly about 4/5 stats were improving due to the constant games he was getting. But then at the back end of the season, he was in decent form, getting average ratings of a little over 7, compared to mid 6's in the early - mid parts of the season. I gave him a new contract to see him through 2 more years and he was also very happy with how we were performing in the league (better than expectations). For some reason though his value started to drop avery fortnight or so, and by the end of the season it had levelled out to £55k. Surely given the form, length of contract remaining, general happiness and my AssMan rating him as a decent League One keeper, he should have been valued quite a bit more, more like the £120k he peaked at earlier in the season even when he weren't playing great?

In case you're interested we finished 8th when the media predicted 16th, but I jumped ship to Swansea at the end of the season.

It appears I've stumped you all!! Never known the forum lost for words to a genuine problem before lol

Maybe the more he played the more people could gauge his potential and worked out he wasn't worth as much as they initially thought??!

I dunno, lol

Maybe he hit his CA mark and as his abilities were leveling out (could even have being yo-yoing a bit) his value was changed to reflect it.