December 4, 1988, Bill Wood traded career Minor League player Todd McClure to the Minnesota Twins for Mark Portugal.
Portugal would pitch five wonderful years in Houston, posting a 52-30 record and a 108 ERA+. In Minnesota he had been a below average pitcher, but after coming to Houston he suddenly became above average and I don't mean slightly above average. I mean well above average. Sure his career 108 ERA+ is slightly above average but in three of those five years he posted an ERA+ of at least 124.
Granted the two 120 seasons he had he pitched just over a 100 innings, however, in his best season he pitched over 200 innings and that was thankfully in Houston.
In 1993 Portugal pitched a career high 208 innings and posted a 139 ERA+, also a career high. He made 33 starts that years and posted an 18-4 record. Portugal would be allowed to enter free agency after the 1993 season. The new general manager at the time, Bob Watson, apparently didn't think enough of Portugal to resign him after his career season.
Smart move by Watson, who saw Portugal sign with San Francisco. In the season and a half with the Giants Portugal posted a 99 ERA+. He would have somewhat of a rebound with Cincinnati but never posted numbers as good as he did with Houston.
Overall Portugal was the prototypical average pitcher at the Major League level. Houston was lucky enough to get some above average years from him.