Yeah, sort of. A position player impacts roughly 10% of his teams at bats and depending upon the position played, roughly that amount in the field (ie, the number of times a ball might be hit to him). But that fielding contribution probably is inflated, as many outs are recorded by strikeout, and many plays are just routine that any player would be expected to make. So I would say defensively an individual player really only impacts 2% of his team's fielding plays.
But since there is offense and defense, that pretty much means a position player impacts 5% of the game offensively and 1% of the game defensively. So 6% of an individual game. Since starting pitchers pitch every 5 games, a position player over 5 games would score 6-6-6-6-6 = a score of 30. If someone wanted to argue that a really good player would impact a game at a rate of 7% instead, that would get the position player up to a score of 35 over 5 games.
Starting pitchers obviously do nothing in 4 games out of 5. But in the one game they play, they have a huge impact. Say a decent starter pitches 7 innings on average. That's 78% of the game while on defense. Pitchers rarely have much impact on offense, so count that as 0. So the average of those two would be 39%. That starter would then have an impact score of 0-0-0-0-39 = 39 total over 5 games. Adding an average of a third of an inning to the stud pitcher's average workload per game, and the pitcher's score would be almost 41 over 5 games.
Bottom line, even though position players could impact every game, in a five game stretch, there may not be as much difference in the impact between a position player and a top notch starting pitcher (and the pitcher could actually have a greater impact). I realize this is a very simplistic break down and there are other components to the game (base running, throwing, moving runners along, etc.), but as an example to illustrate how much impact there is, I think it's not that far off base.