An honest assessment would state that the timing couldn't be much worse. Both Mike Davis (hernia) and Jaxon Shipley (hip) are coming back from surgeries. Kendall Sanders won't play in the season opener after he was charged with a DWI this past spring. Fellow sophomore and expected rotation player Cayleb Jones transferred out of the program.
But the biggest blow might simply be this: Marcus Johnson was putting together one of his best strings of football as a Longhorn. The sophomore was gaining in confidence seemingly by the day, and was making the most of the absences of Davis and Shipley by pulling in big catch after big catch. He's somebody with a bright future in the Longhorn program, and while an MCL strain certainly won't change that from a long-term perspective, it does stink to see Johnson get sidelined after such a nice hot streak.
On a short-term perspective, the Longhorns should be fine as long as Davis and Shipley recover as expected. Both are anticipated as Day One starters, so the Longhorns could get past the absence of Sanders and Johnson if both are ready to go. That would likely leave the Longhorns starting Davis and Shipley on the outside, with Daje Johnson potentially starting in the slot, with guys like Bryant Jackson, John Harris and the freshmen — especially Jacorey Warrick — providing depth. Remember, with the Longhorns' up-tempo scheme, Longhorn wide receiver coach Darrell Wyatt wants five to six receivers that he can rotate through.
The bottom line is that Johnson's injury isn't a death knell. Texas should be almost -go after Sanders returns from suspension, and while there isn't a specific timetable, the injury doesn't appear to be serious enough to keep Johnson out for the entirety of the season, nor serious enough to hamper his long term growth.
In the shorter term, there will be some shuffling, as Johnson was almost certainly in the group of receivers who would provide depth behind expected starters Davis, Shipley and Sanders. But mostly it just stinks that Johnson, who was coming closer and closer to his potential, likely won't be ready to go at the start of the season.