Thomas told Sky Sports: "It's been a difficult series for the guys. I've been proud to play with them because we never gave up at any point in the series.
"We let New Zealand back into the match a bit. If you concede turnover ball against this side you'll get punished. They take their chances.
"The commitment on this tour has been great. We haven't had the amount of preparation Clive wanted or enough time together, but we're not making any excuses because the All Blacks deserved to win the series."
Umaga led the New Zealand charge with a superb two-try salvo that made up for the error of his eighth minute sin-binning, and the centre declared it was job done - even if it was not the spectacle he had hoped for.
He told Sky Sports: "We're very happy to win the series. There were a lot of changes to both sides and there was some weary rugby out there.
"It may not have been the greatest rugby after what we've seen over the last two weeks but we came here to win and that's what we did. We'll enjoy this victory.
"The penalty count was frustrating and we'll have to look at that. The Lions were tenacious and never gave up, which was what we expected. They played like true Lions."
Umaga paid tribute to outstanding debutant fly-half Luke McAlister, who completed the impossible by almost emulating the injured Dan Carter's stunning performance last Saturday.
He added: "Luke McAlister really shone through. It's great for New Zealand rugby to have a player like him coming through. Dan Carter was brilliant in the second Test but Luke was probably just as good."