Marquis started three games for Arizona, pitching to a 9.53 ERA and 2.29 WHIP in 11 1/3 innings before being granted free agency in October.
Walters is now No. 12 on Washington's Top 20 Prospects list and is on the Nationals' radar as a switch-hitting infielder with emerging power.
Walters was born in Cheyenne, Wy., but he went to Cimmaron-Memorial High School in Las Vegas. He hit .549 with 24 stolen bases as a junior.
He went to the University of San Diego and hit .314 with 125 hits in his college career. Those statistics included batting against flame-throwing San Diego State pitcher Stephen Strasburg, his current teammate.
The D-backs selected Walters in the ninth round of the 2010 First-Year Player Draft.
Beginning his career at Class A Short-Season Yakima, Walters hit .302 in 297 plate appearances, all at shortstop. The following season, he played 97 games for Arizona with its Class A South Bend team. Once again, he hit .302. Among his 109 hits were 27 doubles, six triples and nine home runs. He served notice of his powerful bat.
After moving to Washington's Class A Advanced Potomac club following the summer trade, Walters kept it going. He hit .293 in 126 plate appearances, resulting in a combined season average of .300.
In his first Spring Training with the Nationals, Walters sustained a hand injury that slowed the beginning of his season. Upon his return, Walters played at three classifications, hitting a combined .266 while playing for Potomac, at Double-A Harrisburg and at Triple-A Syracuse.
It was this past season that really put Walters on the map. He hit 29 home runs at Syracuse. But he struck out 134 times in 521 plate appearances. With the exception of 27 games he played at third base, most of his 134 games were played at shortstop.
Walters is 6-foot-2, 220 pounds. My first look at him came in the 2011 Arizona Fall League. He did not have the greatest season, hitting .249 in 83 at-bats.
Walters has a compact swing with power generation from an athletic frame that includes strong arms and a solid trunk. His hands are quick through the ball. He has enough speed to selectively steal bases.
In September this season, Walters was promoted to the Nationals. When I saw him start at shortstop, he looked aggressive at the plate, swinging at pitches he felt he could drive. He finished the season with three hits in nine plate appearances, and he did not strike out.
Walters does, however, need to improve his walk rate and swing at fewer fringe pitches. His pitch selection should improve with experience.
While Walters shows segments of five tools, arm strength may be his strongest skill. He has an extremely strong and accurate arm. Walters' arm strength can overcome less overall range than one might like in a shortstop.
The Nationals are established in their starting infield. If the need arises, however, the athletic Walters can play second base and third base as well as shortstop. I think his best role is as a versatile utility player at each of those three positions. With his power and ability to hit from both sides of the plate, his value increases.