Techniques are provided for inline deduplication based on a number of physical blocks having common fingerprints among multiple entries of a buffer cache. One method comprises storing input/output operations in a first cache comprising a plurality of entries each corresponding to a physical storage entity comprising a plurality of physical blocks. A given entry is maintained in the first cache based on a first number of physical blocks of the given entry having a duplicate fingerprint with at least one physical block of another entry in the first cache. A second number can be determined of the physical blocks of each entry having a fingerprint in a second cache, and a first ratio is determined for two entries in the first cache using the second number and the first number. A comparison of the first ratios can be performed to sort and possibly evict entries in the first cache based on the comparison.