...players are more likely to have been born in the earlier months of the year than in the later months.

【答】这是be likely to do sth. 句型：“可能做某事”。如果不定式的动作，早于现在的are，就要使用完成体。即：be likey to have done sth.

不定式是非谓语，要么使用to be born，要么使用to have been born，但不能使用 was born。

类似用法：

If organic compounds are present on Mars, they are more likely to have been preserved in ice.

如有机化合物出现在火星上,他们更有可能早就被保存在冰内。

We are happy to have been invited to their party. 

很高兴我们被邀请参加他们的派对。