The first round of the NBA playoffs is complete, and let's hope the Charlotte Hornets were watching. They were bounced from the Play-In, thereby removing their chance to learn about the postseason firsthand. But if they watched the first round, they learned some valuable lessons secondhand. Siza (and matchups) matters Philadelphia 76ers center Joel Embiid (21) drives against the Charlotte Hornets | Bill Streicher-Imagn Images Karl-Anthony Towns. Joel Embiid. Rudy Gobert. What do these three have in common? They're in the second round because their team was a nightmare matchup for its opponent, or the opponent just didn't have a matchup for them. The Atlanta Hawks didn't have the size to deal with Towns, and doubling him didn't remotely work. The Boston Celtics certainly didn't have the size to deal with Embiid (and the Hornets know well that they don't either). The Denver Nuggets couldn't break Gobert's defense or the length and defense of the rest of the Minnesota Timberwolves.…