I am looking for some help regarding the 3 sentences below: to make sure the commas are correctly placed.
1. “We had a lot of players last year that were coming to the end of their careers and this year we have a lot of young players, who maybe have a point to prove.”
2. Despite being back in the team recently, Masson has found this season to be one of a stop-start nature for himself, especially as he picked up a long-term injury in the Lothian Thistle replay, which kept him out of the side for a number of weeks.
3. Jason Holt and Andy Halliday got in the faces of Ross and McGowan, which meant Dundee couldn’t settle and weren’t given any space to play their normal game.
Thanks in advance. I always get mixed up with who and which and the use of commas
Formal texts tend to use 'heavier' punctuation than informal ones. I'll assume formal here. You may find it useful to know that while the terminal full stop marks the boundaries between successive sentences, the comma, semicolon and colon mark boundaries within a sentence. Those boundaries may be items in a list, relative clauses, ideas, coordinations and so on. Taking your three examples, then:
1. "We had a lot of players last year that were coming to the end of their careers, and this year we have a lot of young players who maybe have a point to prove."
In that example, I'd insert a comma after "careers" because you're referring to two separate time periods (last year and this year) and two separate situations. Next, you have a relative clause (underlined) which appears to be of the integrated (restrictive/defining) kind meaning that no comma is required. It's only the team's young players who may have a point to prove, not just players in general. The information is presented as an integral part of the larger message; it plays an essential role in defining exactly which players maybe have a point to prove.
2. Despite being back in the team recently, Masson has found this season to be one of a stop-start nature for himself, especially as he picked up a long-term injury in the Lothian Thistle replay which kept him out of the side for a number of weeks.
In that example, you've correctly marked off the adjuncts with commas, but the relative clause is again of the integrated (restrictive/defining) kind, so a comma is not required. It's restrictive because the information it provides is essential to our understanding why Masson had a stop-start season.
3. Jason Holt and Andy Halliday got in the faces of Ross and McGowan, which meant Dundee couldn’t settle and weren’t given any space to play their normal game.
3. looks fine to me. The underlined relative clause is non-restrictive this time. The information it provides is non-essential, supplemental, and not part of the larger message, so setting it off with a comma is correct.