The area's leading closer converted 6 of 7 save opportunities

[capcap23]

The area's leading closer converted 6 of 7 save opportunities to help the Golden Eagles win 19 games and make an appearance in a regional title game. He allowed only 3 earned runs in 28 innings pitched, all in a spot start on short notice against Cary-Grove. source

I can't make sense out of the underlined part. Is the letter 's' possession or 'is'? My guess is possession but still it doesn't make any sense to me.

 

[GoesStation]

"Closer" (with a voiced /z/ sound) is a noun in this sentence, and the apostrophe-s is a possessive. The sentence describes a successful baseball player in the pitcher position.

 

[Tarheel]

I would say the league's leading closer

A closer is a pitcher who closes (finishes) a baseball game for his team. He is chosen for that role because he good at getting outs. The closer usually comes into the game when the team is ahead but not by much.