Shields was the Senators' 15th-round pick in the June, 1969 draft, out of Northwestern State (LA). Although he did not pitch professionally in 1969, he apparently attended some kind of workout/extended spring training after signing and was photographed in a 1968 Senators uniform. (We know that the Senators wore the red 1969 uniforms during Spring Training 1970, not the older blue ones. [See John Roseboro's Senators picture, for example])
After two indistinguished seasons in the Senator/Ranger chain, Shields went 8-9, 3.39 at Pittsfield (AA) in 1972 and won an invite to 1973's training camp. Despite arming himself with Funky Frames™, sideburns, and a deep tan (all perfect to go with Ranger doubleknits), Shields was sent out to AAA Spokane, where he bombed (1-9, 5.89) and was cut.
Note: the first picture is misidentified as "John Shaw, 1968" in a current eBay auction. However, the only contemporaneous "John Shaw" was a 2nd baseman in the Yankee chain from 1970-1972. (And besides, you can see part of the name "Shields" in the 3rd picture.)