Per the article, “He’s definitely improving,” Panthers coach Matt Rhule said of Mayfield. “He gets more and more of a feel of what he can do at the line of scrimmage. What he’s done in 10 days is pretty impressive — or 10, 11 practices. He’s making really good jumps.” Mayfield would add stability to the skill position group like Darnold would not. This is good news for the WR group.
Russell Gage has had some knocks against his fantasy value in the last couple of weeks, most notably the signing of free agent Julio Jones. Gage was at least walking off the field, so one would assume this isn't a long-term injury, but we'll have to wait and see. If he misses some time, and should Chris Godwin also miss time to begin the season, Jones may be in for WR2 treatment.
The article would go on to mention that Lock had "appeared to be the better quarterback in the scrimmage." Neither option is genuinely going to affect the skill positions in Seattle positively, but it would be nice to know the starter for late-round 3-QB builds on Underdog and deep Superflex leagues. Lock is the better option to potentially offer DK Metcalf and Tyler Lockett a little more upside.