Valentine was one of a trio of young Expos outfielders (with Andre Dawson and Warren Cromartie) for whom stardom was predicted in the late 1970s. Only Dawson met those expectations. Valentine had two straight 25-HR, 76-RBI seasons (1977-78; .293, .289) as Montreal’s everyday right fielder and hit two inside-the-park homers in Olympic Stadium in 1977. In 1978 he led NL outfielders with 24 assists, winning a Gold Glove; in 1979 he had 21 HR and a career-high 82 RBI. But on May 30, 1980 he was hit in the face with a pitch by Roy Thomas of the Cardinals and was out 40 days with a fractured cheekbone. Larry Parrish had injured his wrist earlier that month, and the two injuries probably cost the Expos the pennant. Valentine could have been on his way to his best season: He finished with a .315 average, 67 RBI, and 13 HR in just 86 games.
In 1981 Valentine hit just .208 and was traded to the Mets at the end of May for Jeff Reardon and Dan Norman. He hit .280 in 1982, but his power was gone. He hit only 8 HR in 1982 and 13 for the Angels in 1983.