Johnny Manziel Tatted and Skinny at Vegas Pool Party

While RG3 is taking over the reins in Cleveland, ex-Browns QB Johnny Manziel was raging in Vegas this weekend -- looking skinnier and more tatted than ever.

Check out these pics of Manziel at a Wet Republic pool party at the MGM Grand -- where witnesses say he partied and boozed for hours ... but that's not really surprising at this point.

You can see how much Manziel's appearance has changed since he was drafted -- back in 2014, his body was essentially inkless and more jacked.

Clearly, things have changed.