Pierce roasted Tayshaun the previous three years. Scoring 22+ points, 7+ boards and shooting 50+% from the floor (actually 46% in 04-05).
Tayshaun is a fine defender who'll cause Pierce some problems but he can't limit Paul the way James did. LeBron's defense below the three point line on Paul Pierce was simply immense, he stopped Pierce on his usual mid post action. James was quicker, stronger, taller, bigger (bulk), longer, and better. Tayshaun is slower, weaker, taller, smaller (bulk), longer and worse. Prince has some advantages his way but Pierce has more than enough areas to attack him at. Prince will be vulnerable to Pierce's strength, his ability to muscle his way into the paint of the mid post. His reach will make the shot difficult though.
As Bankshot pointed out, Pierce has defended Tayshaun very well, I'd say better than Tay has defended Paul.