As istrasci and rintaun correctly point out,
サッカー選手でもあります has similar meaning as
サッカー選手です. But it is true that
ある is not the same word as
です. What they don't explicitly point out and is crucial is that the
ある used here is not a predicate. It is comparable to the English
- A is a soccer player
- A is smart
In the sentences above, you can tell that the predicate is the noun/adjective phrase following
be but is not
be itself (in other words,
be is not contributing to the meaning) from the fact that they can be used retaining their meaning, without
- I consider A a soccer player
- I consider A smart
On the other hand,
be in the following examples are used to express existence, and is a predicate.
- I think, therefore I am
- There is a soccer player
The animacy restriction on Japanese
いる only concerns the predicate usage (the usage meaning existence or posession). While the following
いる are in the predicate usage,
ある is not.
- A はサッカー選手である
Therefore, your example is a case where the animacy distinction is irrelevant.
Furthermore, as is well known, even the predicate
ある can be used with animate subjects.
- A には子供がある
The distinction between
いる is actually much more complicated than mere animacy opposition.