Puppa was very good – on ability not far off Tom Barrasso (both very big, athletic goalies for their time) and with an even more injury-plagued career than Barrasso. Interestingly, he forced the trade of Barrasso in 1988 by outplaying him for the Sabres.
Injuries basically ruined his career. When he was healthy – first half of the 1988-89 season before breaking his arm, 1989-90 when he was a Vezina Finalist, 1993-96 with Tampa when he basically carried that team to their early success and probably should have won the 1996 Vezina - he was a full-on elite NHL netminder. Top 3-5 guy in the sport.
But he was just plagued by injuries and poor luck – broke his arm twice, had major back issues throughout his career, and missed substantial time with a few knee injuries as well. His career completely lost momentum from 1990-93 because of those injuries, and then back problems ended his career post-1996.