您没有发送需要解析的请求，您需要添加

def start_requests(self):
        starts_urls = ['https://www.transfermarkt.nl/heracles-almelo/kader/verein/1304/saison_id/2022/plus/1']
        for url in starts_urls:
            yield scrapy.Request(url=url, callback=self.parse)

您有一个打字错误。您将start_urls写成了starts_urls。

编辑：

您可能需要更改的另一件事是删除get()。

import scrapy

class TransferMarketScraper(scrapy.Spider):
    name = 'transfermarket'
    start_urls = ['https://www.transfermarkt.nl/heracles-almelo/kader/verein/1304/saison_id/2022/plus/1']

    def parse(self, response):
        for player in response.css('div.grid-view table.items tbody tr'):
            #player number
            try:
                player_number = int(
                    player.css('div.rn_nummer::text').get().strip()
                )
            except ValueError:
                player_number = 'NA'
            except AttributeError:
                continue

            yield {'player_number': player_number}