You ask:
Is the statement "a basketball is a physical object" a contradiction?
At first glance, yes, but we can eliminate the contradiction by pointing out a distinction that has been argued about for more the 2,500 years. By adopting language to deal with universals and particulars we can eliminate the paradox that our intuitions tell us exists. (The physical basketball is a "particular" of the idea or concept of a physical basketball, itself the "universal".) Hang on to your hat for some philosophical jargon from the philosophy of language.
Your first example is a correspondent truth. We accept that there exists a physical object, and that the language corresponds or refers to the object. In the language of Frege and his ideas of Sinn und Bedeutung, in modern philosophy of language, we would say that the token 'basketball' refers to the referent, physical basketball in the world. That is, the reference is more or less the correspondent truth that aligns language, to borrow from Wittgenstein, to the state of affairs in the world. We might refer to that basketball as an extension.
The second example is a little more complicated and controversial, but Frege used the term sense and while there is quibbling over the details in the literature, the sense might be thought of as the idea or concept of a thing, or a collection of its properties that form the intension. Rather than something physical, it refers to the properties that inhere to what we are "pointing at" with the word. It refers to an abstractum. We can think of this as Aristotelian essence if it helps, though again, things can become controversial. Is it a contradiction to refer to an idea as physical?
No, if you understand that a physical basketball (a particular) is abstracted towards a category represented by 'physical basketball', a piece of language that denotes a collection of things with the same property (a universal). Historically in philosophy, whether or not the latter thing exists is known as the problem of universals. Note that we can resolve the apparent paradox by separating our tokens by representing one token without delimiters and the other with:
A 'physical basketball' is a phrase that represents a physical basketball in the world.
This resolves the contradiction by pointing out that sometimes in language, we use language to mention things ('physical basketball'), and sometimes we are using the language (physical things), and is called use-mention distinction. This distinction also helps to resolve the traditional debate between Platonists who were realist and argued that the mention was somehow real and nominalists who argued the mention was just language, obviously in favor of the nominalists. The failure to recognize use-mention distinction can often lead to woo or hilarity as the late Dennett points out in his video on deepities (YT).
So, like many paradoxes, when we create a framework of language to address some fine distinctions, we dissolve it and are left with an important philosophical distinction. You'll come across different views regarding this issue over the history of philosophy, and many have restated the problem in different ways. Ogden and Richards in their Meaning of Meaning, for example, extend Frege's thinking using the terms 'symbol', 'reference', and 'referent'. And the infamous Quine addressed the issue and took a unique ontological stance too while introducing the terminology 'ontological commitment' which is handy in discussing these matters. For more terminology that is useful, also read WP's "De dicto and de re".