Clearly Gen. McClellan would be the go-to general to pull from the bullpen if Gen. McDowell’s Army of the Potomac proves unable to get the job done.
Right, "Little Mac" is a rising star... but... notice his three big victories so far -- Philippi, Rich Mountain & Corrick's Ford.
In every case McClellan's forces outnumbered Confederates more than 4 to 1, and McClellan benefitted from capable Union commanders under him, notably Rosecrans.
This may help explain why, later, McClellan will constantly exaggerate Confederate strengths in hopes of extracting more troops from President Lincoln for his own army.
McClellan knew it was numbers as much as tactical brilliance which won his early battles in West Virginia.