Here are the sentences using the correct tenses:
- They have just met their opponents. (Present Perfect)
- You haven't played your best game yet. (Present Perfect)
- I had bought the tickets by the time of their arrival. (Past Perfect)
- I visited a game of cricket when I was in London last year. (Past Simple)
- The coach talked to him yesterday. (Past Simple)
- I have just written an email to the sponsor. (Present Perfect)
- According to legend, the ancient Olympic Games are said to be founded by Heracles, the son of Zeus. (Present Simple Passive)
- I have participated in two competitions since I began exercising. (Present Perfect)
- We have already heard the news about your wins. (Present Perfect)
- Over 10,000 athletes took part in the Olympic Games last year. (Past Simple)