the role of “in what”

[Yuta]

I do not clearly understand the role of “in what” in this sentence. (line 4)

I think “in what” ＝ ”which” here. correct?

The Los Angeles Angels reinstated outfielder Mike Trout from the injured list and slotted him in as their center fielder and No. 2 hitter on Friday against the Detroit Tigers in what served as his first game since July 12.

 

[emsr2d2]

You can read it as "the thing that" or, in this case, "the game that".

 

[jutfrank]

You can read it as "the thing that" or, in this case, "the game that".

You mean "in the thing/game that".

 

[emsr2d2]

You mean "in the thing/game that".

Sorry. I do. I thought the OP was simply asking what the role of "what" is, rather than "in what".