Hello Taraneh,
While I can understand your logic for putting the dates into the header tag to try and influence and reduce duplicate data issues the header title tag really tend to work best when it is a bit more focused. Hence why you probably tend to see a improvement when you just target specific keywords such as "home team vs away team" etc.
I don not feel that the word "preview" would become too repetitive as does actually describe the content well. As would "post match report" etc
To reduce the issues have you considered using the mark-up schema for articles with published dates or maybe even periodical articles. Periodical articles could possibly allow you to have multiple fixture all tagged with a period(volume), in your case each season. This could hopefully allow Google to identify each article as a stand alone item that could be different from season to season.
More information on article schema can be found here
Hope that helps a little.