Vladimir Guerrero spent the first eight years of his career in the National League where he hit an absurd .318/.379/.553 with a 148 OPS+. Luckily, this meant he didn’t have many opportunities to increase Mike Mussina’s ERA and WHIP. In those eight years, the peak of Guerrero’s career, he only faced Mussina twice, in 1998 and again in 1999. Mussina held him hitless in six at-bats.
Guerrero joined the Angels as a free agent in the winter of 2003 and spent the last half of his career pulverizing American League pitching. The A.L. version of Guerrero couldn’t run and field the way he had in Montreal but he was still a menace with the bat. His six-year batting line in Anaheim is nearly identical to his one in Montreal (.319/.381/.546 with a 141 OPS+). While in the A.L. Mussina also managed to keep Guerrero’s bat at bay. Here’s a yearly accounting of their encounters