Signed by the Philadelphia Phillies as an amateur free agent in 1981, LaValliere started out as a third baseman but was converted to catcher in 1982. He was sent to the St. Louis Cardinals during the 1984 season as part of a conditional deal. Signing with the Cards as a free agent in 1985, Spanky spent two years with the club, which included a trip to the World Series. Excellent at throwing out potential base stealers, he won a Gold Glove award in 1987.
In spring training of the 1987 season, LaValliere was traded to the Pittsburgh Pirates alongside Andy Van Slyke and Mike Dunne in exchange for fellow catcher Tony Pena. Spanky and Van Slyke would later become stalwarts on the hugely successful Pirates teams of the early 1990s, when Pittsburgh went to three consecutive National League Championship Series from 1990-1992. Unfortunately for the Pirates, they lost in all three of their NLCS appearances, in 1990 to the eventual World champion Cincinnati Reds and in 1991 and 1992 to the Atlanta Braves. In the 1992 NLCS, LaValliere was involved in the famous final play of Game 7, as Atlanta first baseman Sid Bream Slid beneath his tag to score the Series-winning run for the Braves.
During the 1993 season, LaValliere was released by Pittsburgh, and signed a contract with the Chicago White Sox. The White Sox won the American League West division title, but lost in the ALCS to the eventual World champion Toronto Blue Jays. Spanky would spend two more seasons in Chicago before retiring. Spanky's lack of speed was a frequent source of parody on ESPN's Baseball Tonight. In particular, a stopwatch was used to clock Spanky going around the bases. Furthermore, former major leaguer Andy Fox's home run trot was faster than Spanky going from first to home.