Play is an essential component of childhood, but parents and educators sometimes view it as an optional add-on, which gets in the way of learning. This view persists in spite of evidence that play is helpful and sometimes critical to learning in multiple domains, perhaps because precise mechanisms whereby play occasions learning are not well understood. Here, I propose a new research perspective on playful learning, which might fill this gap, and solidify our understanding of both play and learning: a focus on comparison and structural alignment. Comparison (and structural alignment, which highlights useful comparisons) is a well-studied learning mechanism, and it occurs often during free and guided play. Do we learn through play because we compare during play? I briefly summarize the learning benefits of comparison and sketch the ways in which play may trigger comparison. I then list several concrete research questions, through which we may inspect the role of comparison in mediating between play and learning.