I agree that it seems unlikely would keep the capitol at Moscow (or at least keep it as the sole capitol), but I'll stick to the initial supposition. Early losses against Sweden would have prevented him from St Petersburg, but he might have moved the capitol elsewhere.
If St Petersburg isn't built as a major city and isn't used as the capitol it remains a port of only moderate size.
The capitol remaining in Moscow makes it harder for Petr to retain a Western focus and his efforts to modernize are more resisted and hindered.
With less focus (and strength) North, Russia will likely have more trouble with Sweden and let them, the Poles, and the Lithuanians fight it out. Petr may then turn more of his efforts South around the Crimea.
In general, without the move to St Petersburg (which assumes some success against Sweden), Russia is limited in the North and West. Russia also emerges somewhat more backward than IOTL.